John 3:6

That which is born [τ ο γ ε γ ε ν ν η ε ν ο ν]. Strictly, that which hath been born, and consequently is now before us as born. The aorist tense (3, 4, 5, 7), marks the fact of birth; the perfect (as here), the state of that which has been born (see on 1 John 5:18, where both tenses occur); the neuter, that which, states the principle in the abstract. Compare ver. 8, where the statement is personal : everyone that is born. Compare 1 John 5:4, and 1 John 5:1; 1 John 5:18.

Of the flesh [ε κ τ η ς σ α ρ κ ο ς]. See on ver. 14. John uses the word sarx generally, to express humanity under the conditions of this life (i. 14; 1 John 4:2; 1 John 4:3; 1 John 4:7; 2 John 1:7), with sometimes a more definite hint at the sinful and fallible nature of humanity (1 John 2:16; John 8:15). Twice, as opposed to pneuma, Spirit (John 3:6; John 6:63).

Of the Spirit [ε κ τ ο υ π ν ε υ μ α τ ο ς]. The Holy Spirit of God, or the principle of life which He imparts. The difference is slight, for the two ideas imply each other; but the latter perhaps is better here, because a little more abstract, and so contrasted with the flesh. Spirit and flesh are the distinguishing principles, the one of the heavenly, the other of the earthly economy.