Albert Barnes Commentary John 21:17

"He saith unto him the third time, Simon, [son] of John, lovest thou me? Peter was grieved because he said unto him the third time, Lovest thou me? And he said unto him, Lord, thou knowest all things; thou knowest that I love thee. Jesus saith unto him, Feed my sheep." — John 21:17 (ASV)

The third time. It is probable that Jesus asked this question three times because Peter had denied Him three times. Thus He tenderly admonished him of his fault and reminded him of his sin, while He solemnly charged him to be faithful and vigilant in fulfilling the duties of the pastoral office.

The reason why the Savior addressed Peter in this manner was doubtless because Peter had just denied Him—had given a most sorrowful example of the instability and weakness of his faith, and of his tendency to fall. As Peter had thus been prominent in forsaking Him, He took this occasion to give him a special charge and to secure his future obedience.

Therefore, He administered the charge in such a way as to remind Peter of his fault, and He made him so prominent as to show the Savior's concern that from then on Peter might not be left to dishonor his high calling. This same charge, in substance, He had on other occasions given to the apostles (Matthew 18:18), and there is not the slightest evidence here that Christ intended, as the Papists pretend, to give Peter any peculiar primacy or eminence in the church.

The charge to Peter arose, clearly, from his prominent and sorrowful act in denying Him, and was the kind and tender means used by a faithful Savior to keep him from similar acts in the future dangers and trials of life. It is noteworthy that the admonition was effective. From then on, Peter was one of the most firm and unwavering of all the apostles, and thus fully justified the name of a rock, which the Savior by anticipation had given him (see the notes on John 1:42).