John 6:28

What shall we do? Gr. ti poiomen? “what should we be doing?” The present tense may be understood to imply that the Jews were inquiring regarding a habitual way of life rather than any isolated act. In this they were correct, as is indicated by Jesus’ answer in v. 29. Their question was a tacit recognition that they realized Jesus’ words were an indictment of their religious life in general.

Works of God. These words are found also in Jer. 48:10 (the LXX has the plural as here), where they refer to works desired by God. The Jews’ concept of true religion was to a large extent in terms of works, and so it was natural that in inquiring how they might please God, they asked as to what works they might do.