John Lightfoot on John 21:3

[I go a fishing.] Christ had ordered his apostles to meet him at a mountain in Galilee, Matthew 28:16. It is plain, verse 14, that he had not yet appeared to them there: so that it is something strange how they durst keep away from that mountain, and how the four newly mentioned durst be absent from the rest of their number. They knew the mountain without doubt; and if they knew not the time wherein Christ would make his appearance amongst them, why should they not abide continually there in attendance for him?

It should seem, that they did not look for him till the Lord's day, which had not yet been since they were come into Galilee. And perhaps the sons of Alpheus had, in their return from Jerusalem, betaken themselves amongst their relations, determining to be at that mountain on the Lord's day. These seven dwelt not far off the mountain, which was near Capernaum, and hard by the sea of Galilee: only Nathanael, who dwelt more remote in Cana, towards the extreme north parts of that sea. He was not yet gone home, but, waiting the appointed time, stayed here. Peter and Andrew dwelt in Capernaum, and so, probably, did James and John: Philip in Bethsaida, and Thomas (as we may conjecture from his Greek name Didymus) probably lived amongst the Syro-Grecians in Gadara, or Hippo, or some place in that country of Decapolis, not very far from Gennesaret.