"The works which the Father has given Me to finish—the very works that I do—bear witness of Me" (John 5:36).
Up to this point, Jesus has taught that there were two witnesses concerning His Sonship: first, He witnessed concerning Himself, and second, John the Baptist testified of Him. In verse 36, He tells of a third witness: the works His Father commissioned for Him to do. Generally, these included His works of obedience in fulfilling the demands of the law and His intercession between God and man. But more specifically, Jesus was referring to His miracles.
The Pharisees had witnessed His healing of the man at Bethesda. If they had really known their Old Testament Scripture, they would have realized that Jesus was a man sent from God because no one could perform such acts unless God were with Him. Nicodemus had it right when he admitted this very thing: “No one can do these signs which you do unless God is with him.”
The miracles were not a testimony by themselves. Jesus’ teaching His words, always took the priority. Yet, the miracles were necessary as evidence concerning Jesus identity, given to support His claims. God did not leave His people without evidence. While His Word was certainly sufficient, He provided tangible evidence concerning Jesus’ nature and purpose. Yet, the Pharisees still did not believe.
Many atheists today claim that they would believe in the existence of God if they could have some proof of His existence. If they could only be given some evidence, or if only they could see a miracle, they would then finally confess that they had been wrong. But God has provided evidence. When Jesus lived on earth, He performed many miracles, which have been recorded in the Scriptures. God has provided proof concerning His existence in the very make-up of our beings—we have consciences that testify to His holy law (Rom. 2). The creation itself, by its majesty and complexity, testifies of Him (Rom. 1, Ps. 19). Yet they still do not believe.
God has testified concerning Himself, and still the scoffers refuse to glorify Him. And they will continue in their unbelief until God sends His Word into their hearts by the power of His Spirit and creates new life where there was once only darkness.
While it is valid to argue for the existence of God using the proofs He has provided, remember that faith comes not by seeing evidence but by a changed heart. Only when the Gospel is proclaimed and the Spirit is active in renewing the soul will any come to faith. Pray specifically today for an unbeliever you know.