18 And Jesus, walking by the Sea of Galilee, saw two brothers, Simon called Peter, and Andrew his brother, casting a net into the sea; for they were fishermen.
19 Then He said to them,“Follow Me, and I will make you fishers of men.”
20 They immediately left their nets and followed Him.
21 Going on from there, He saw two other brothers, James the son of Zebedee, and John his brother, in the boat with Zebedee their father, mending their nets. He called them,
22 and immediately they left the boat and their father, and followed Him.
Simon … and Andrew (v.18) — They had met Jesus on an earlier occasion in Judea (John 1:40-42) where they had probably gone to be baptized by John the Baptist.
Luke 5:1-11 seems to be an account of a different occasion.
So it was, as the multitude pressed about Him to hear the word of God, that He stood by the Lake of Gennesaret, and saw two boats standing by the lake; but the fishermen had gone from them and were washing their nets. Then He got into one of the boats, which was Simon’s, and asked him to put out a little from the land. And He sat down and taught the multitudes from the boat. When He had stopped speaking, He said to Simon, “Launch out into the deep and let down your nets for a catch.” But Simon answered and said to Him, “Master, we have toiled all night and caught nothing; nevertheless at Your word I will let down the net.” And when they had done this, they caught a great number of fish, and their net was breaking. So they signaled to their partners in the other boat to come and help them. And they came and filled both the boats, so that they began to sink. When Simon Peter saw it, he fell down at Jesus’ knees, saying, “Depart from me, for I am a sinful man, O Lord!” For he and all who were with him were astonished at the catch of fish which they had taken; and so also were James and John, the sons of Zebedee, who were partners with Simon. And Jesus said to Simon, “Do not be afraid. From now on you will catch men.” So when they had brought their boats to land, they forsook all and followed Him.
It could be that … between this first call of Matthew and the call in Luke, the early disciples continued to fish for a time and not until the call in Luke 5 did they forsake all. While Matthew’s gospel indicates that they followed Jesus, there is no clear statement that they left their fishing occupation for good. — Walvoord, page 38.