The fourth watch — The Jews (as well as the Romans) usually divided the night into four watches, of three hours each. The first watch began at six, the second at nine, the third at twelve, the fourth at three in the morning. If it be thou — It is the same as, Since it is thou. The particle if frequently bears this meaning, both in ours and in all languages. So it means, John 13:14, John 13:17. St. Peter was in no doubt, or he would not have quitted the ship.
Related Commentaries of Matthew 14:25
Matthew 14:25
25 And in the fourth watch of the night Jesus went unto them, walking on the sea.