Theophylact of Bulgaria
Had He claimed, "I perform this through My own authority," they would have stoned Him as an adversary of God. Conversely, if He had stated, "I perform this by the power of God," they could have turned the people against Him, as it would imply that He identified Himself with the Divine. Therefore, the Lord strategically presents them with John's question, doing so with clear intention and without deceit.