John 1:21

he being asked openly and plainly, professed, and did not dissemble nor halt in his speech. These negatives are in Scripture often added to affirmatives, to exclude all exceptions, Job 5:17 Psa 40:10-12. But confessed: he did not tell them once so, but again and again, because many were musing about it, Luk 3:15. I am not that great Messiah which God hath promised you, and in the expectation of whom you live, Luk 2:26,38 Lu 19:11 Joh 4:25. The diligence we shall constantly observe in the servants of God in holy writ, to avoid the arrogating of that honour to themselves which is due only to God and Christ; and this, together with John’s steadiness and plainness, doth very well become all professors, but the ministers of the gospel especially.

Verses 19-28 John disowns himself to be the Christ, who was now expected and waited for. He came in the spirit and power of Elias, but he was not the person of Elias. John was not that Prophet whom Moses said the Lord would raise up to them of their brethren, like unto him. He was not such a prophet as they expected, who would rescue them from the Romans. He gave such an account of himself, as might excite and awaken them to hearken to him. He baptized the people with water as a profession of repentance, and as an outward sign of the spiritual blessings to be conferred on them by the Messiah, who was in the midst of them, though they knew him not, and to whom he was unworthy to render the meanest service.