Jesus wanted His hearers to see that their unbelief went deeper than a rejection of Him. They trusted in Moses (John 5:45), yet Jesus says, "had ye believed Moses, ye would have believed me: for he wrote of me" (John 5:46). Gill explains that they believed the books to be Moses' writings and the word of God, "and yet did not believe the things contained in them, respecting Christ." Barnes puts the logic simply: if they would not credit what Moses wrote, which they professed to believe, "it is not to be expected that you will believe my declarations." The question presses them to face the gap between what they claimed to honor and what they actually believed.

The answer is implied in the question: if they would not believe Moses, they would not believe Jesus. No reply from His hearers is recorded. Jesus' discourse ends here, and the next chapter begins, "After these things Jesus went over the sea of Galilee" (John 6:1). Earlier John had said that the Jews "sought the more to kill him" (John 5:18).

The Jews of Jesus' day held Moses in the highest regard as the giver of the Law; Jesus calls him the one "in whom ye trust" (John 5:45). "His writings" refers to the books of Moses.

Barnes and Gill both point to places where Moses wrote of the Messiah: the seed of the woman who would bruise the serpent's head (Genesis 3:15), the promise that in Abraham all families of the earth would be blessed (Genesis 12:3), Shiloh, to whom the gathering of the people would be (Genesis 49:10), and the Prophet like Moses whom Israel must hear (Deuteronomy 18:15).

This question shows that the scriptures and Jesus speak with one voice. Jesus had already said of the scriptures, "they are they which testify of me" (John 5:39). To reject Him is to misread Moses, and to truly read Moses is to be led to Him.

This is a sobering question for anyone who respects the Bible. Matthew Henry's Concise Commentary warns that many trust in a form of doctrine without entering into its real meaning, just as the Jews did with Moses. Honoring Scripture means letting it lead us where it points.