Simon Peter saith—I go a fishing.— I am going a fishing. Heylin. Our Lord having, first by the angels, and then in person, ordered his disciples to go home to Galilee, with a promise that they should see him there, it is reasonable to think that they would depart as soon as possible; (see the second reason assigned in the note on John 21:1.) wherefore, when they were come to their respective homes, they followed their occupations as usual, and particularly the apostles, who pursued their old trade of fishing on the lake. Here, as they were plying their nets, one morning early, Jesus shewed himself to them.
Related Commentaries of John 21:3
John 21:3-4
3 Simon Peter saith unto them, I go a fishing. They say unto him, We also go with thee. They went forth, and entered into a ship immediately; and that night they caught nothing.
4 But when the morning was now come, Jesus stood on the shore: but the disciples knew not that it was Jesus.