And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up: that whosoever believeth in Him should not perish but have eternal life. – John 3:14,15

Our Lord began, in the third chapter of John’s gospel, by telling Nicodemus that he must be born again, and explaining to him the mysterious character of the new birth. Whereupon Nicodemus was filled with wonder, and unbelievingly exclaimed, “How can these things be?” He does not seem to have made the smallest advance towards faith by hearing of the new birth, and therefore on the selfsame occasion our Lord turned aside from the doctrine of regeneration, the inner work, to speak to him of the doctrine of faith, or the work of Christ, which is the object of saving faith. Thus it comes to pass that the very same chapter which has in it that searching passage, “Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God,” contains also these encouraging words, “As Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up: that whosoever believeth in Him should not perish, but have eternal life.” …If we can with all boldness and distinctness declare the inward work which the Holy Ghost accomplishes in the soul by working in us to will and to do of God’s good pleasure, and at the same time can tell the sinner most plainly that the object of his faith is not the work within, but the work which Jesus Christ accomplished upon the cross for him, we shall have dealt faithfully with divine truth, and wisely with our hearer’s soul. The faith which brings salvation, looks away from everything that is inward to that which was accomplished and completed by our once slain but now ascended Lord; and yet no man has this faith except as it is wrought in him by the quickening Spirit. If we can preach both these truths in harmonious proportion, it seems to me that we shall have hit upon that form of Christian teaching which, while it is consistent with truth, is also healthful to the soul. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0755.cfm