Though they had toiled to no purpose all night, yet at Christ’s command they are willing to renew their toil, knowing, that by relying on him, their strength should be renewed as work was renewed upon their hands. Observe, reader, we must not presently quit the callings in which we are engaged, because we have not the success in them which we promised ourselves. The ministers of the gospel in particular must continue to let down their nets, though they have, perhaps, toiled long, and caught nothing. They must persevere unwearied in their labours, though they see not the success of them. And in this they must have an eye to the word of Christ, and a dependance thereupon. We are then likely to have success, when we follow the conduct of Christ’s word.
Christ intended by the multitude of fishes, which he would make Simon catch, to show him the success of his future preaching, even in cases where little success was reasonably to be expected.
[Excerpt from the Benson Commentary]