John Calvin Commentary Acts 27:38

"And when they had eaten enough, they lightened the ship, throwing out the wheat into the sea." — Acts 27:38 (ASV)

And when they had eaten enough. This circumstance does show that they were finally moved by Paul’s words. It was not yet light, so they could not know whether there was any haven near. And yet they cast out into the sea the wheat which remained, that they might lighten the ship. They would not have done this unless Paul’s authority had greater influence with them now than before. But as all unbelievers are unstable, that persuasion quickly vanished from their minds.