Ye have sent to John, and he hath borne witness to the truth. The sending to John was probably a reference to the official transaction described in John 1:19. This is not the "other" whom he referred to, for in the next clause he made solemn disclaimer of resting his claim upon John or upon any individual man.
The witness of the forerunner was a true one. The function of the prophet is to bear witness to the Light, to strip off the veils which hide it, to call attention to its most solemn realities, to quicken vision, to stimulate conscience, to disturb apathy, to discern the coming and prepare the way of the Lord (see John 1:4, John 1:5, notes), He was not the Light; but he did call attention to a testimony immeasurably more precious than any word proceeding merely from human lips.
The testimonies of John, both before and after he came into contact with Christ, were very wonderful and were adapted to exert and did produce a deep impression upon the people for a time; but by themselves they would not have given sufficient ratification to the Lord's words.
We may welcome still all Johannine, ministerial testamonies to the Lord. but the power of God himself must assert itself to the inner consciousness bet, re any man receives the gospel. No mere human testimony to such claims as these rises to the dignity of the occasion.
Unless the Father's witness can be discerned, supreme, convincing, and final, John's witness would be insufficient. It may arrest attention, it may impress the apathetic, it may overawe the gainsayers; but it is not final, nor does it leave the hearers without excuse.
All the rhetoric, all the threatening, all the irony, of Elijah would have failed if the fire of the Lord had not fallen to consume the sacrifice.