John Gill Commentary John 21:14

"This is now the third time that Jesus was manifested to the disciples, after that he was risen from the dead." — John 21:14 (ASV)

This is now the third time
Or day of Christ's appearance to his disciples: he appeared to them first on the same day he rose, and then a second time eight days after, or that day a week later, and now at the sea of Tiberias; for within this compass of time he had made more appearances than three, though to particular persons, and not to such a number of the disciples as at these three times:

that Jesus showed himself to his disciples after that he was risen
from the dead :
and thus, as by the mouth of two or three witnesses, everything is established; so by these three principal appearances of Christ to his disciples, his resurrection from the dead was confirmed.