Zacharias here foretells what came to pass about thirty years after, for it cannot be thought that John began his ministry before the sacerdotal age, especially considering Christ did not begin sooner, Luk_3:23.
Thou shalt be called the prophet; that may either signify, thou shalt be a prophet, as Mat_5:9Joh_1:12; or thou shalt be owned or taken notice of as the prophet
of the Highest. Both were true in John. He was a prophet, (though not that Prophet, Joh_1:21), yea, and more than a prophet, saith our Saviour, Mat_11:9.
For thou shalt go before his face to prepare his ways. This was according to the prophecy, Isa_40:3Mal_4:5: and according to what John said of himself, Mat_3:3Mar_1:3. See Poole on "Mat_3:3".