Witness. The subject is introduced abruptly, but rises naturally out of the circumstances. The claims made, if less than the author represents them, were such as to raise the question of authority. By what authority could He substantiate them? In the first place, John the Baptist, in whose teaching the people for a time took such pleasure. His chief witness is God Himself, whose testimony is declared through the works which He enables Jesus to do, and also directly in Scripture, which they study in the hope of gaining life. And yet they reject the Prophet, whom Moses in those very Scriptures (cf. Deuteronomy 18:15 ff.) and many others foretold.
John 5:30-40
30 I can of mine own self do nothing: as I hear, I judge: and my judgment is just; because I seek not mine own will, but the will of the Father which hath sent me.
31 If I bear witness of myself, my witness is not true.
32 There is another that beareth witness of me; and I know that the witness which he witnesseth of me is true.
33 Ye sent unto John, and he bare witness unto the truth.
34 But I receive not testimony from man: but these things I say, that ye might be saved.
35 He was a burning and a shining light: and ye were willing for a season to rejoice in his light.
36 But I have greater witness than that of John: for the works which the Father hath given me to finish, the same works that I do, bear witness of me, that the Father hath sent me.
37 And the Father himself, which hath sent me, hath borne witness of me. Ye have neither heard his voice at any time, nor seen his shape.
38 And ye have not his word abiding in you: for whom he hath sent, him ye believe not.
39 Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.
40 And ye will not come to me, that ye might have life.