IN THOSE DAYS, walking by the Sea of Galilee, Jesus saw two brothers: Simon who is called Peter, and Andrew his brother, casting a net into the sea, since they were fishermen. And Jesus said to them, “Follow Me, and I will make you fishers of people.” Immediately, they left their nets and followed Him. As He went from there, Jesus saw two other brothers: James son of Zebedee and his brother John, in a boat with their father Zebedee, mending their nets. And He called them. Immediately, they left the boat and their father, and followed Him. Jesus traveled throughout Galilee, teaching in their synagogues and proclaiming the Gospel of the Kingdom, and healing every disease and every sickness among the people.
Saint Gregory the Great comments on how much did the fishermen leave behind,
Someone may wonder: At the Lord's beckoning, what or how much did these fishermen, who scarcely had anything, leave behind? On this, my beloved, we should attend to one's intention rather than one's wealth. That person has left behind a lot who keeps nothing for himself, who, though he has little, gives up everything. We tend to be attached to those things we own, and those things we scarcely own, we carefully hold on to. Therefore, Peter an Andrew left much behind when they left behind covetousness (greed) and the very desire to own. That person has left much behind who renounces with the thing owned the very coveting of that thing. Therefore, those poor who followed Jesus left behind just as much as those less poor who did not follow Him but were able to covet. So when you notice that some have left a great deal behind, you need not say to yourself, 'I want to imitate those who disdain this world, but sorry, I have nothing to leave behind.' You will leave much behind, if you renounce earthly desires. External things, however small they may be, are sufficient for the Lord, since He looks at the heart and not at our material goods. Nor does He judge by how much is involved in our sacrifice but from how much it is made. For if we judge by external goods, our holy merchants traded in their nets and vessels for the perpetual life of the angels.