New birth is a term commonly used to convey concisely the truth brought out in the beginning of John 3, namely, that a man’s origin spiritually must be of God’s work in him if he is to come under the moral sway of God in grace. This is specially the point in the conversation of the Lord with Nicodemus: “Except a man be born again [ἄνωθεν, not only again, but “anew,” a new source and beginning], he cannot see the kingdom of God.” “Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God”: that is, born of the Holy Spirit as the power, and of water (the word) as the means of moral cleansing. “Of His own will begat He us with the word of truth” (James 1:18; compare Eph. 5:26). “That which is born of the Spirit is spirit”; it is of the nature of its source—spiritual and not natural.
Nicodemus was astonished at what he heard, yet as a teacher in Israel he should have known the “earthly” (not “worldly”) things concerning the kingdom of God. He should have learned from such passages as Ezekiel 36:25-28 and Jeremiah 31:33, that new birth was necessary for Israel to have part in God’s kingdom. The heavenly things of Christianity are spoken of subsequently in John 3 as the fruit of the cross, and the love of God, but there must be new birth as the foundation in man, whatever be the nature of the blessing proposed.