Of water and of the Spirit – To the baptism of water a man was admitted when he became a proselyte to the Jewish religion; and, in this baptism, he promised in the most solemn manner to renounce idolatry, to take the God of Israel for his God, and to have his life conformed to the precepts of the Divine law. But the water which was used on the occasion was only an emblem of the Holy Spirit. The soul was considered as in a state of defilement, because of past sin: now, as by that water the body was washed, cleansed, and refreshed, so, by the influences of the Holy Spirit, the soul was to be purified from its defilement, and strengthened to walk in the way of truth and holiness.
When John came baptizing with water, he gave the Jews the plainest intimations that this would not suffice; that it was only typical of that baptism of the Holy Ghost, under the similitude of fire, which they must all receive from Jesus Christ: see Mat 3:11. Therefore, our Lord asserts that a man must be born of water and the Spirit, i.e. of the Holy Ghost, which, represented under the similitude of water, cleanses, refreshes, and purifies the soul. Reader, hast thou never had any other baptism than that of water? If thou hast not had any other, take Jesus Christ’s word for it, thou canst not, in thy present state, enter into the kingdom of God. I would not say to thee merely, read what it is to be born of the Spirit: but pray, O pray to God incessantly, till he give thee to feel what is implied in it! Remember, it is Jesus only who baptizes with the Holy Ghost: see Joh 1:33. He who receives not this baptism has neither right nor title to the kingdom of God; nor can he with any propriety be termed a Christian, because that which essentially distinguished the Christian dispensation from that of the Jews was, that its author baptized all his followers with the Holy Ghost.
Though baptism by water, into the Christian faith, was necessary to every Jew and Gentile that entered into the kingdom of the Messiah, it is not necessary that by water and the Spirit (in this place) we should understand two different things: it is probably only an elliptical form of speech, for the Holy Spirit under the similitude of water; as, in Mat 3:3, the Holy Ghost and fire, do not mean two things, but one, viz. the Holy Ghost under the similitude of fire – pervading every part, refining and purifying the whole.