Now as he walked by the sea of Galilee
 The same with the sea of Tiberias, ( John 6:1 ) , 
 he saw Simon:
 whose surname was Peter, the son of Jonas: 
 and Andrew his brother;
 the brother of Simon, 
 casting a net into the sea;
 of Galilee, in order to catch fish: 
 for they were fishers:
 by occupation, this was their trade and business, by which they got their livelihood; (See Gill on Matthew 4:18).