The man went away and told the Jews that it was Jesus who had healed him.
There are no small number of expositors that attribute an act of betrayal to this man due to this passage. They believe he is trying to save himself from trouble by pointing to Jesus as the responsible party for his sabbath violation. But I don’t think that is what is happening.
First, the Jews had asked the man in verse 12 “who told you you to take up your bed and walk?” (apparently oblivious to the fact that a miracle had happened). But here in verse 15, he doesn’t introduce Jesus as the one that told him to pick up his mat and walk, but rather, he introduces Jesus as the healer.
In verse 14 Jesus told this man not to sin any more. This man was to be holy. But for some reason it is believed that when this man told the Jews who had healed him, he had violated some sort of agreement with Jesus not to tell anyone.
That might have been the case in Luke 5:
While he was in one of the cities, there came a man full of leprosy. And when he saw Jesus, he fell on his face and begged him, “Lord, if you will, you can make me clean.” And Jesus stretched out his hand and touched him, saying, “I will; be clean.” And immediately the leprosy left him. And he charged him to tell no one, but “go and show yourself to the priest, and make an offering for your cleansing, as Moses commanded, for a proof to them.
But there’s no indication that Jesus wanted this man to keep quiet about what had happened to him. After all, that would have been impossible given the very public nature of this miraculous event. Even in Luke 5, Jesus commanded the healed leper to go and tell the religious leaders (ie, the priests) of what had happened.
This man recognized Jesus’ authority and significance when he picked up his mat and carried it away. Up to this point in John’s story, the only hostility we see involving Jesus is when Jesus is driving people out of the temple with a whip. I don’t see what evidence this man would have had that the religious authorities would have been hostile toward Jesus (at least, not at this point in time).
And it’s probably true that there is some degree of self-interest here. After all, the allegation was that this man had violated the sabbath. That’s a serious allegation. But this was an unusual circumstance, and God’s law has provisions for exceptional circumstances. By appealing to Jesus, this man is showing that he did nothing wrong.
The man departed, and told the Jews.—We are not told what reason underlay his report to the Jews. It is natural that he should give the answer which he could not give before (John 5:13), and that he should wish to secure himself from the charge of Sabbath-breaking by supplying his authority. The narrative does not suggest that he did this in a tone of defiance, which has been found here from a remembrance of John 9, still less that he used his new strength immediately to bring a charge against the Giver of it. The impression is rather, that he felt that this power came from a prophet sent by God, and that he told this to those who were God’s representatives to the nation, supposing that they would recognize Him too. – Ellicott
In the temple – The man seems to have gone at once to the temple – perhaps a privilege of which he had been long deprived. They who are healed from sickness should seek the sanctuary of God and give him thanks for his mercy. Compare the notes at Isaiah 38:20. There is nothing more improper, when we are raised up from a bed of pain, than to forget God our benefactor, and neglect to praise him for his mercies. – Barnes Notes
Barnes makes an excellent point that even those today whom suffer from debilitating sickness can relate in their inability to gather corporately in worship. Ryle also draws the same conclusion as the two above:
There is no proof that the man did this with an evil design. Born a Jew and taught to reverence his rulers and elders, he naturally wished to give them the information they desired and had no reason to suppose, for anything we can see, that it would injure his Benefactor.