John Chrysostom — as excerpted in the Catena Aurea on John 21:15-17

“(Hom. lxxxviii) The question asked for the third time disturbed him: Peter was grieved because He said unto him the third time, Lovest thou Me? He was afraid perhaps of receiving a reproof again for professing to love more than he did. So he appeals to Christ Himself: And he said unto Him, Lord, Thou knowest all things, i. e. the secrets of the heart, present and to come.”