Albert Barnes on John 6:28

What shall we do, that we might work the world's of God? That is, such things as God will approve. This was the earnest inquiry of men who were seeking to be saved. They had crossed the Sea of Tiberias to seek him; they supposed him to be the Messiah, and they sincerely desired to be taught the way of life; yet it is observable that they expected to find that way as other sinners commonly do--by their works. The idea of doing something. to merit salvation is one of the last that the sinner ever surrenders.