Then the mariners were afraid, and every man cried out to his god. And they threw the cargo that was in the ship into the sea to lighten it for them. But Jonah had gone down into the innermost parts of the ship, and he was laying down and was fast asleep. Bible

“to lighten it for them.” Although the versions differ as to how to translate this, the sailors threw the cargo over to lighten the load “for them,” that is, the sailors saw the cargo as a huge danger to them and the ship, so for their own sake they threw it overboard.

Commentary for: Jonah 1:5