Charles Ellicott Commentary John 10:38

"But if I do them, though ye believe not me, believe the works: that ye may know and understand that the Father is in me, and I in the Father." — John 10:38 (ASV)

But if I do, though you do not believe me, believe the works.—A higher faith would have believed Him. Had they truly known their own spiritual needs, and truly known the meaning of that great truth He had taught, they would have found in Him the true satisfaction of the mind’s cravings, and the faculty of faith would have rested in the object of its existence.

For all this the Old Testament had been a preparation, but their minds had not been prepared by it. He will therefore take their own lower ground and appeal to the sight of those who do not have faith. (Compare to Note on John 20:29.)

Let them test the works, think of their character, as some of them had already done (John 9:16), and see at least that these are of the Father.

That you may know, and believe, that the Father is in me.—The more probable text is, that you may perceive, and may (permanently) know that the Father is in Me... Failing the intuitive faith-knowledge, He appeals to the intellectual perception—which is not immediate but from which they may ascend to that knowledge—and may then really know that such works can only be of the Father; and that, therefore, the Father is present in Him who does them, and that He who does them is one with the Father (John 10:30).