Our Lord Jesus in John 21 tells the apostle Peter to feed His sheep three times. What role was Peter being told to assume? Is it that of an elder? Which sheep was our Lord talking about? Is it the other apostles and disciples or the church that was going to be established at Jerusalem? What did He expect of Peter?
See "By the Sea of Galilee." Peter had denied the Lord three times and apparently continues to be despondent over his failure. Jesus gives him three opportunities to declare his love for him, but Peter has gotten more cautious. Jesus asks for agape (a love of devotion and service) and Peter offers phileo (the love of a close and dear friend). Still, Jesus gives him tasks that will build his faith. He tells Peter to feed his lambs, tend his sheep and to feed his sheep.
Jesus' sheep are all Christians, both Jews and Gentiles (John 10:14-16). Jesus is the Shepherd and we follow him. "I am the good shepherd. The good shepherd gives His life for the sheep" (John 10:11).
We aren't talking about physical sheep, so also the action of feeding is not a physical one. Jesus is instructing Peter to give spiritual nourishment. It is an imagery God has used often. "And I will give you shepherds according to My heart, who will feed you with knowledge and understanding" (Jeremiah 3:15).
Lambs are young sheep, so lambs well represent new Christians. "As newborn babes, desire the pure milk of the word, that you may grow thereby" (I Peter 2:2). Peter's job was to teach God's word to help new Christians to grow.
He was also to tend the sheep. Again, this imagery was used before. "He also chose David His servant, and took him from the sheepfolds; from following the ewes that had young He brought him, to shepherd Jacob His people, and Israel His inheritance. So he shepherded them according to the integrity of his heart, and guided them by the skillfulness of his hands" (Psalms 78:70-72). It is true that this is a job of elders. "Therefore take heed to yourselves and to all the flock, among which the Holy Spirit has made you overseers, to shepherd the church of God which He purchased with His own blood. For I know this, that after my departure savage wolves will come in among you, not sparing the flock" (Acts 20:28-29). Peter did fill the role of an elder along with being an apostle. "The elders who are among you I exhort, I who am a fellow elder and a witness of the sufferings of Christ, and also a partaker of the glory that will be revealed: Shepherd the flock of God which is among you, serving as overseers, not by compulsion but willingly, not for dishonest gain but eagerly; nor as being lords over those entrusted to you, but being examples to the flock; and when the Chief Shepherd appears, you will receive the crown of glory that does not fade away" (I Peter 5:1-4).
Peter was not being placed at the head of the other apostles. Such counters what Jesus had long taught them. They had always fought over who would be greatest, and thus missed the point. "There arose also a contention among them, which of them was considered to be greatest. He said to them, "The kings of the nations lord it over them, and those who have authority over them are called 'benefactors.' But not so with you. But one who is the greater among you, let him become as the younger, and one who is governing, as one who serves. For who is greater, one who sits at the table, or one who serves? Isn't it he who sits at the table? But I am in the midst of you as one who serves" (Luke 22:24-27). In John 21, Jesus was giving Peter instructions on how to serve, not to rule. And this Peter did. "Beloved, I now write to you this second epistle (in both of which I stir up your pure minds by way of reminder), that you may be mindful of the words which were spoken before by the holy prophets, and of the commandment of us, the apostles of the Lord and Savior" (II Peter 1:12-21).