What does Mark 1:20 mean?

James and John had gone fishing with Simon Peter the night before and come back without a bite. Then they'd seen the enormous catch that Jesus had arranged for them (Luke 5:1-7). Beyond the miracle of the huge amount of fish after a night of nothing, it's interesting to note that Jesus provided the fishermen with the support to be able to leave (Andrew and Simon Peter their business, and James and John their father) so they could follow Jesus with limited earthly worries—at least in that moment. Jesus didn't always do this. He told the rich young ruler to give away his riches as a discipline of putting Jesus first (Matthew 19:16–23), and he told another man not to wait until his father was dead to pursue discipleship (Matthew 8:21–22).

Again, Mark emphasizes Jesus "immediately" called James and John. These brothers left their father Zebedee in the boat with the hired servants and followed Jesus. Their bold faith stands out as an example to those today who likewise must often leave behind people and security to pursue Jesus and His calling on their lives.

In this verse, we are also left without answers in some areas. First, we are not told whether Zebedee supported his sons' decision. Second, we are never told what happened with their family business. Did it survive or wither away? Was the family in financial trouble as a result? Their bold faith is shown as a risk with many unknowns. However, the full account of Mark's Gospel reveals a decision that was worth the risk. These men experienced miracles no other person would see, hear teachings from the Son of God, and truly become "fishers of men" through the lives they changed after following Jesus during His years on earth.