Whoever claims to be speaking for God must prove that what he says is true. In other words, what he hears from God and proclaims must come to pass as proof it is from God. There must always be a manifestation proving that what is spoken is really from God.
A long time ago, when a prophet gave a word of prophecy, the only way people knew it was true is when it came to pass. If the prophecy did not come to pass, it became obviously that it was not from God and the one who spoke that word was stoned to death. Today, this may seem uncivil, but in those days it purged out the worst of religious practices.
Now, the true test of a prophet is that what he says comes to pass. Prophets who were sent from God as recorded in the Old Testament prophesied the coming of Christ and it came to pass. Jesus’ entire life on earth was predicated on the fulfillment of God’s prophetic word. In his ministry, when a paralyzed man was brought to him, he commanded healing, something not easy to do unless God was in it.
In Mark 2:9 Jesus says, “Which is easier, to say to the sick of the palsy, Thy sins are forgiven; or to say, Arise, and take up thy bed, and walk”(ASV). It is obvious that it is not easy to bring about a miracle of healing in someone’s body, but if anyone does it and it comes to pass, God is really in it. It has to be God healing a sick person since the work itself is far beyond human ability. It is God who does the supernatural work and not man.
Now, by performing a miracle for the man with paralysis, Jesus proved the word he spoke was obviously hard to say, but he said it anyway knowing he was authorized and it came to pass. An ordinary person without a relationship with God can not do what Jesus did because such a one is not authorized. This proves that his authority is from above because the Father sent him and by being sent his authority is legitimate.
In John 9:33, when another man who was healed by Jesus was questioned as to whether Jesus himself was truly someone approved of God, he just said, “If this man were not from God, he could do nothing”(ASV). It is true, if someone is not sent from God, he can do nothing.