He was not that light
He was a light; he was the forerunner of the sun of righteousness, the "phosphorus" of the Gospel day; he had great light in him; he knew that the Messiah was ready to come, and declared it; and upon his baptism he knew him personally, and signified him to others: he had great light into the person and work of Christ; and into the way of salvation by him, and remission of sins through him; into the doctrines of faith in Christ, and of evangelical repentance towards God; and into the abolition of the legal Mosaic and Jewish dispensation; and was an instrument of giving light to others; yea, he was a burning and shining light, in whose light the Jews rejoiced, at least for a season: but then he was not that light, the word and wisdom of God; that uncreated light that dwelt with him from all eternity; nor that which was the light of men, from the creation; nor that light, which was of old promised to the saints and patriarchs of the Old Testament, and shone in the ordinances and predictions of that state; nor that fountain and giver of light, of every sort, to men; not that light in which is no darkness, and always shines; not that true light, or sun of righteousness, the Messiah, or that lightens every man that comes into the world:
but was sent to bear witness of that light;
which is repeated, to distinguish him from that light; to show what he was sent for, and that he acted according to his mission; and to express the honourableness to his work.