We must enquire how John, who is a prophet and more than a prophet, who made known the Lord when He came to be baptized, saying, “Behold the Lamb of God, that taketh away the sine of the world! — why, when he was afterwards cast into prison, he should send his disciples to ask, “Art thou he that should come, or look we for another?”
Did he not know Him whom he had pointed out to others; or was he uncertain whether this was He, whom by foretelling, by baptizing, and by making known, he had proclaimed to be He?
Ambrose, Ambros., in Luc 7:19: Some understand it thus; That it was a great thing that John should be so far a prophet, as to acknowledge Christ, and to preach remission of sin; but that like a pious prophet; he could not think that He whom he had believed to be He that should come, was to suffer death; he doubted therefore though not in faith, yet in love. So Peter also doubted, saying, “This be far from thee, Lord; this shall not be unto thee.” [Matt 16:22]
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Hom in Ev. vi. 1