When Jesus was confronted by a group of hostile Jews in John 5, he proceeded to prove his claim as the Son of God by bringing to their attention four credible witnesses whom testified on his behalf.
Jesus knew they would never be satisfied with his testimony alone and neither would God’s law (Deuteronomy 19:15).
The first witness: John the Baptist
Ye sent unto John, and he bare witness unto the truth. But I receive not testimony from man: but these things I say, that ye might be saved. He was a burning and a shining light: and ye were willing for a season to rejoice in his light. (John 5:33-35)
On the day John baptized Jesus, he saw Christ approaching and proclaimed, “Behold the Lamb of God, which taketh away the sin of the world” (John 1:29). Even though John had already been imprisoned, a short time before he was seen as a credible prophet.
The second witness: The miracles of Jesus
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. (John 5:36)
Many of the Jews undermined his miracles and debated whether a sinner–as they believed Jesus to be–could do such things (John 9:16). But as Nicodemus admitted, those miracles were actually proof that Jesus was the Christ (John 3:1-2).
The third witness: God the Father
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. And ye have not his word abiding in you: for whom he hath sent, him ye believe not. (John 5:37-38)
On the day of his baptism, God the Father spoke from heaven to confirm his Son, Jesus (Matthew 3:16-17). However, as Jesus alluded, they could not hear the voice of God either due to the hardness of their hearts or their willful ignorance.
The fourth witness: The Old Testament of the Bible
Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me. And ye will not come to me, that ye might have life. I receive not honour from men. But I know you, that ye have not the love of God in you. I am come in my Father’s name, and ye receive me not: if another shall come in his own name, him ye will receive. How can ye believe, which receive honour one of another, and seek not the honour that cometh from God only? Do not think that I will accuse you to the Father: there is one that accuseth you, even Moses, in whom ye trust. For had ye believed Moses, ye would have believed me: for he wrote of me. But if ye believe not his writings, how shall ye believe my words? (John 5:39-47)
Jesus instructed them to search the scriptures–the Old Testament–because it is full of the new covenant (Jeremiah 31:31). Of course, that new covenant is centered upon Christ and the work he would accomplish on the cross (Luke 22:20).
The new covenant–the gospel of Jesus Christ–was a controversial topic among the Jews in that it made Gentiles heirs to the promises of God (Matt. 8:11-12, Galatians 3:7, Galatians 3:29). As a matter of fact, the promise of the gospel dates back as far as Abraham’s first calling (Genesis 12:2-3, Galatians 3:8). In short, even the Old Testament is all about Jesus.