4 What is the meaning then of this obscure question? May that Sun shine upon us, from which that lamp derived its flame. And so the resolution of it is altogether plain. John had separate disciples of his own; not as in separation from Christ, but prepared as a witness to him. For meet it was that such an one should give his testimony to Christ, who was himself also gathering disciples, and who might have been envious of Him, for that he could not see Him. Therefore because John's disciples highly esteemed their master, they heard from John his record concerning Christ, and marvelled; and as he was about to die, it was his wish that they should be confirmed by him.
For no doubt they were saying among themselves; Such great things does he say of Him, but none such of himself. “Go then, ask Him;” not because I doubt, but that you may be instructed. “Go, ask Him,” hear from Himself what I am in the habit of telling you; you have heard the herald, be confirmed by the Judge. “Go, ask Him, Are You He that should come, or do we look for another?” They went accordingly and asked; not for John's sake, but for their own. And for their sakes did Christ say, “The blind see, the lame walk, the deaf hear, the lepers are cleansed, the dead are raised, the poor have the Gospel preached to them.”
You see Me, acknowledge Me then; ye see the works, acknowledge the Doer. “And blessed is he whosoever shall not be offended in Me.” But it is of you I speak, not of John. For that we might know that He spoke not this of John, as they departed, “He began to speak to the multitudes concerning John;” the True, the Truth Himself, proclaimed his true praises.
Source: Sermons on Selected Lessons of the New Testament (New Advent)