Matthew Poole and continuators on John 3:6

6 That which is born of the flesh , is flesh ; and that which is born of the Spirit, is spirit .

That which was born of natural Flesh; for flesh sometimes signifies the Man. So the Prophet saith, All flesh is grass; so Gen. 6.12. All flesh, that is, all men had corrupted their way. Or, That which is born of corruption, from vitiated and corrupted Nature; (so flesh is oft taken in Scripture, Rom. 8.4, 5, 8, &c.)

is flesh, that is, it bringeth forth effects proportionable to the cause; a man purely natural brings forth natural Operations. Man, as man, moveth, and Eateth, and Drinketh, and Sleepeth. Corrupted man brings forth vitious and corrupt fruit, which often are called the works of the flesh, Gal. 5.19. Flesh here signifieth the whole man, whether considered abstractly from the adventitious corruption of his Nature, or as fallen in Adam, vitiated and debauched through Lust.

But that Man o[illegible: 1 letter] Woman who is regenerated by the Spirit of Grace, is spiritual; he is after the Spirit, Rom. 8.5. he is one Spirit with God, 1 Cor. 6.17. he is made partaker of the Divine Nature, 2 Pet. 1.4. he doth not commit sin, 1 Ioh. 3.9. Nothing in Operation exceedeth the virtue of that cause which influenceth it; so as no man from a meer natural Principle, can perform a truly spiritual Operation; and from hence 'tis absolutely necessary that man must be born of the Spirit, that he may be qualified for the Kingdom of Heaven.