The word leader(s) appears just 4 times in the NASB relating to Christians in the New Testament.
Leaders in Matthew 23:10
Then Jesus spoke to the multitudes and to His disciples, saying, "The scribes and the Pharisees have seated themselves in the chair of Moses; therefore all that they tell you, do and observe, but do not do according to their deeds; for they say things, and do not do them. And they tie up heavy loads, and lay them on men's shoulders; but they themselves are unwilling to move them with so much as a finger. But they do all their deeds to be noticed by men; for they broaden their phylacteries, and lengthen the tassels of their garments. And they love the place of honor at banquets, and the chief seats in the synagogues, and respectful greetings in the market places, and being called by men, Rabbi. But do not be called Rabbi; for One is your Teacher, and you are all brothers. And do not call anyone on earth your father; for One is your Father, He who is in heaven. And do not be called leaders; for One is your Leader, that is, Christ. But the greatest among you shall be your servant. And whoever exalts himself shall be humbled; and whoever humbles himself shall be exalted." (Matthew 23:1-12 NASB)
The Greek word for leader(s) in Matthew 23:10 is the noun kathegetes. It means leader or guide. This word appears nowhere else in the New Testament. Why? Because His disciples obeyed what Jesus told them. Jesus said do not be called Rabbi or leader, do not allow someone to address you with such a title. This scripture warns against using titles associated with teaching (Rabbi, Father, Leader). Jesus clearly said that God is the only one deserving of these distinctions. Jesus said to His disciples "you are all brothers" meaning they are equal in God's family. Note that Jesus did not say "Peter is your leader." Jesus said the greatest among you shall be your servant. Jesus did not say the greatest among you shall be your leader or your servant leader.
These commands prohibit the disciples of Jesus from seeking or receiving titles, producing distinctions among themselves, implying authority to control the opinions and conduct of others, and claiming that others should acknowledge them as superiors. Honorary/religious/spiritual titles are to be avoided by God's people. God forbids us to receive any such reverence. In the kingdom of God there are no titles, special names, given to set someone above the rest. No one was called Pastor Paul, Reverend Peter, Minister John, or Priest James.
What did the writers of the New Testament call themselves if they did not use the titles we have today?
Paul, a bond-slave of Christ Jesus, called as an apostle (Romans 1:1)
James, a bond-slave of God and of the Lord Jesus Christ (James 1:1)
Simon Peter, a bond-slave and apostle of Jesus Christ (2 Peter 1:1)
Jude, a bond-slave of Jesus Christ (Jude 1:1)
The Revelation of Jesus Christ, which God gave Him to show to His bond-slaves, the things which must soon take place; and He sent and communicated it by His angel to His bond-slave John (Revelation 1:1)
All of the New Testament writers that acknowledged themselves as the authors of their writings called themselves bond-slaves or bond-servants of God. It is also worth noting that all of God's people are called His bond-slaves in Revelation 1:1. Bond-slave means one who sells himself into slavery to another, one who gives himself up to the will of another, one who serves another without regard for his own personal interests. The word therefore pictures the absolute submission of a man or woman to their Master. The bond-slave is totally devoted to the loving Master! It is the Master's love and the bond-slave's love for the Master which motivates this full submission. A bond-slave essentially says, "Nothing matters about me, so long as the Lord Jesus is glorified."
Leaders in Luke 22:26
"Behold, the hand of the one betraying Me is with Me on the table. For indeed, the Son of Man is going as it has been determined; but woe to that man by whom He is betrayed!" And they began to discuss among themselves which one of them it might be who was going to do this thing. And there arose also a dispute among them as to which one of them was regarded to be greatest. And He said to them, "The kings of the Gentiles lord it over them; and those who have authority over them are called 'Benefactors.' But not so with you, but let him who is the greatest among you become as the youngest, and the leader as the servant. For who is greater, the one who reclines at the table, or the one who serves? Is it not the one who reclines at the table? But I am among you as the one who serves. And you are those who have stood by Me in My trials; and just as My Father has granted Me a kingdom, I grant you that you may eat and drink at My table in My kingdom, and you will sit on thrones judging the twelve tribes of Israel. (Luke 22:21-30 NASB)
The Greek word for leader in Luke 22:26 is the verb hegeomai. It means to lead or to guide. The word servant here is also a Greek verb which means one who serves. The NASB translates these as English nouns which gives the idea of status rather than action. Jesus is not using the title of leader here (which describes an official position) but rather describing one who leads (which describes an action which can be done by anyone). This would translate best to "Let the one who leads become as the one who serves."
Jesus is much more practical than we think. Christ is our one and only leader. We are not in bondage to obey men. Instead of setting up people in positions as official leaders He gives us all freedom. All followers of Christ can lead, guide, & direct because all of His followers are equal brothers and sisters. Jesus stressed the attitude that even when we are leading, guiding, & directing someone we are to do it as serving and caring. Jesus said that you shall not lord over others. Not so with us! Jesus exemplified this He came in the flesh to serve not to lord over others. The Lord didn't lord over others! We are not to lord over or exercise authority over other Christians in the Kingdom. Jesus did not put the focus on my works (leading) or my status (being a leader) but the needs of others (serving)!
Though Jesus gave the apostles the unique privilege to judge the twelve tribes of Israel in the future they are even equals even in that. Jesus didn't say, "Peter you will be the greatest judge and the rest of you will also judge." In this life they were still equals as well and they are addressed as brothers in verse 32. Remember Jesus is the firstborn among many brethren. He has the unique status as the "firstborn son."
Jesus assures them that His kingdom is established on different principles from those of the world; that his subjects were not to expect titles, and power, and offices in his kingdom. We should not aim at office and power, but to be humble, and serve and help one another. (See this look at the word office in the New Testament if you suppose they exist).
The word "benefactor" is a title of one who bestows "favor/benefit" on another. It was applied to kings by way of "compliment or flattery." So again here Jesus says "not so with you" concerning titles of honor. Should we dare allow ourselves to be given titles or to bestow titles on others when our Lord Jesus Christ came as a servant and humbled himself to the point of death, not just death but death on a cross?
Leaders in Hebrews 13:24
Greet all of your leaders and all the saints. (Hebrews 13:24 NASB)
The Greek word for leaders in Hebrews 13:24 is the verb hegeomai. Again it means to lead or to guide. This verse is best translated as "Greet all of those leading you and all the saints." This does not suggest someone who sits in an office called Leader Ted who never actually leads anyone, is devoid of relationships, and only speaks to them as a crowd.
Leaders in Hebrews 13:17
Similar is my post The Proper Translation of Hebrews 13:17
Obey your leaders and submit to them, for they keep watch over your souls as those who will give an account. Let them do this with joy and not with grief, for this would be unprofitable for you.
Of the four verses that use of the word leader(s) in the NASB this is the one that gets focused on the most by far. Simply by looking at the first two passages above we should recognize something sounds wrong here. Obey and submit to leaders? We already know that Jesus said that we shall not lord over or exercise authority over other children of God and that we are not to be called leaders or accept titles of honor. Does the bible contradict? No the bible does not contradict. The belief of the one man in authority over another hierarchy structure that exists in the church has caused scriptures to be skewed. Three words are mistranslated here: obey, leaders, and submit.
The English word obey means to carry out or fulfill the command, order, or instruction of. It carries the idea of obligation to do what someone else says & failure to obey results in sin. But a word meaning obey does not appear in Hebrews 13:17. The Greek word translated obey here is peitho. Peitho means "to persuade; to be persuaded."
The Greek word for leaders in Hebrews 13:17 is the verb hegeomai. We saw earlier that it means to lead or to guide. Here it is best translated as "those leading you" or "those guiding you." Thus it is not a title of people in positions but a verb describing one who is performing the action of leading.
The Greek word for submit in Hebrews 13:17 is hupeiko. The word means to yield, to give in to. The word only appears once in the New Testament. The Greek word hupotasso is the primary word for submit in the New Testament and is not used here.
Hebrews 13:17 is properly translated as:
Be persuaded by those guiding you, and be yielding; for they keep watch over your souls as those who will give an account. Let them watch over you with joy and not with grumbling, for this would be unprofitable for you.
This is essentially saying to be persuadable, to not be prideful but to be yielding. Allow those with wisdom to guide you to truth. Listen to the trustworthy and don't be rebellious. This verse does not say that there are leaders in positions or offices who we must obey on the basis of their authority. There is ONE LORD, JESUS CHRIST! Those who watch over & guide others are to do so joyfully and willfully not with grumbling. We are not to cause them to grumble by our unwillingness to yield to God's truth.
The verse could also be put as this, "Be responsive to those who guide you. Listen to their counsel. They are those who who are alert to the condition of your lives and work under the strict supervision of God and His truth." There is no guiding or guarding without relationship. If someone is not actually guiding you personally, if that person is not alert to the condition of your life then that person is not keeping watch over your soul! Thus you can't be persuaded by this person because they do not even communicate with you and wouldn't even know if you yielded to them. Those who allow themselves to be called leader or pastor do not lead or shepherd if they do not actually guide and guard. God gives function, gifts, and ministry (ministry means work done for the benefit of others) thus Christians are defined by love and good works not by titles, positions, or power. Christians are defined by action not positions or titles. A follower who is not following is not a follower at all.
The action of leading is a perfectly biblical concept but the freedom of Christ demands that any child of God can lead. Leading is done by serving, that is loving and caring for others. There is no special leader, no unique "man of God." We have one leader Jesus Christ! Modern Christianity is obsessed with leaders of or being leaders of congregations, movements, or groups far more so than being followers of Jesus Christ and servants of others.
The English word leader means, "a person who leads; One occupying the first or foremost position." Leader makes us think of authority. If you are a leader that means you are in charge. God did not set up anyone to be in charge but Himself. We lose our equality and our freedom to function when we exalt other men or ourselves as leaders rather than Christ. We arrogantly claim to be humble by calling ourselves "servant-leaders" thus we think we can ignore Christ's command of putting ourselves above others. Jesus acknowledged Himself as the one true Leader but also said that while on earth He came to serve. We do not need more servant leaders; we need more servants..period! Many leaders don’t mind being called a servant; they just don’t like being treated like one. Jesus washed the feet of His disciples. Jesus Christ humbled himself to the point of death, death on a cross! Do we dare call ourselves humble?
Jesus' example for us runs very deep. Jesus didn't even go around calling Himself Messiah Jesus or Christ Jesus. Though there are many reasons we know that Jesus was often discrete in admitting who He was.
The woman said to Him, "I know that the Messiah is coming; when that One comes, He will declare all things to us." Jesus said to her, "I who speak to you am He." (John 4:25-26)
So they all said, “Are you the Son of God, then?” He answered them, “You say that I am.” (Luke 22:70)
So Pilate asked him, “Are you the king of the Jews?” He replied, “You say so.” (Mark 15:2)
The problem with being called a leader or other religious title is that it is you allowing yourself to be considered greater than others when all of God's children are equals, united in Christ. Being called a servant leader or first among equals is just silly. Every follower of Christ has the same life giving spirit of Christ within them. Exalting men as leaders discourages and disarms. It says, "let the pros handle it." But the pros can't handle it because God never intended them to. God wants all of us to love. Jesus clearly teaches us that accepting titles puffs us up and robs God of His rightful place. Interestingly elders/overseers/shepherds\pastors are the ones who were to observe us to protect us. Instead we observe people who claim to be those very things who know little to nothing about us. God did not intend for leaders to serve while the rest of us observe. He wants all of us to serve because He is our one Leader and we are all brothers.