21:1-3
We now come to the closing chapter of John’s gospel and the third appearance of Jesus to His disciples that John reports. This happens by the Sea of Tiberias and some of the disciples had gone fishing. So the disciples had returned to Galilee. The “sons of Zebedee” are James and John, who were partners with Peter in fishing.
So they all went out to fish, but caught nothing. Night was the preferred time for fishing. Some may think it strange that they went fishing after having seen the risen Christ, but we forget that they had no idea what to do. In Luke 24:49 Jesus tells them to wait in Jerusalem until the Holy Spirit comes on them in power.
21:4-6
In the early morning, after their fruitless fishing trip Jesus stood on the shore. It would have been poor light, and the disciples a little out to sea, so they did not recognise Jesus. As was His custom, Jesus asked them a question, knowing what the answer would be. He asked them if they had any fish, to which the answer was, of course, no. Jesus told them to throw the net over the other side. They did so and had an enormous haul. Remember that in one of their first encounters with Jesus a similar thing had happened (Luke 5:1-11).