Matthew Poole and continuators on John 3:15

15 That whosoever believeth in him, should not perish, but have eternal life .

Here our Lord openeth the Instrumental cause of Iustification and Salvation, that is, believing [non-Latin text not transcribed] in him. It is one thing to believe him as a Teacher, another thing to believe in him as a Saviour. The Object of the first is a Proposition; we believe a Person when we assent and give credit to what he saith, because he saith it. The Object of the latter, is the Person and Merits of the Mediator. As the looking up to the brazen Serpen healed the Person, not by any physical Operation, but from the goodness of God, as it was an act of Obedience to the Divine Institution for that end: So neither doth Faith in the Mediator justifie and obtain pardon for any Soul from any meritorious vertue in that act, but from Gods gracious Ordination, that so it shall be; he hath so ordained, that whosoever should rest upon Christ, and receive him by Faith as his Mediator and Saviour, should not perish, but live for ever. There are other things besides Faith necessary to Salvation, such are Repentance, Love, and new Obedience; nor is Faith onely mentioned, because they are ingredients into it; but because Faith is the root of all those, and that from which they must necessarily slow; for it is as impossible that any should truly hope, and trust in, and rest upon Christ for that life which he hath onely promised to those that obey him; as it is impossible that any should indeed trust in, and rest upon a man who hath promised a reward upon a condition, for that reward, without any care to fulfil that condition. But by this and other places, where Faith alone in Christ is mentioned as necessary to Salvation; Nicodemus was taught, that no Obedience to the works of the Law without this Faith in the Mediator, would bring the Soul to eternal Life and Salvation.

Marginal references: Vers. 36. Chap. 6.47.