Regeneration

You must be born again. (John 3:7)

"Regeneration is a subject which lies at the very basis of salvation, and we should be very diligent to pay careful attention that we really are "born again," for there are many who think they are, but are not.

Be assured that the name of a Christian is not the nature of a Christian; and that being born in a Christian land, and being recognized as professing the Christian religion is of no avail whatsoever, unless there is something more added to it; being "born again" is a matter so mysterious, that human words cannot describe it. "The wind blows where it wants, and you hear the sound of it, but you can't tell where it comes from or where it goes: so is every one that is born of the Spirit." 

Nevertheless, it is a change that is known and felt: known by works of holiness, and felt by a gracious experience. This great work is supernatural. It is not an operation that a man performs for himself: a new principle is infused, that works in the heart, renews the soul, and affects the his entire being.

It is not a change of my name, but a renewal of my nature, so that I am not the man I used to be, but a new man in Christ Jesus. To wash and dress a corpse is a far different thing from bringing it to life: man can do the one, only God can do the other. 

If you have then, been "born again," your acknowledgment will be, "O Lord Jesus, everlasting Father, you are my spiritual Parent; if your Spirit had not breathed into me the breath of a new, holy, and spiritual life, I would have been 'dead in trespasses and sins'  to this day. My heavenly life is wholly derived from you, it is attributed to you. My life is hidden with Christ in God. "It is no longer me who lives, but Christ who lives in me." May the Lord enable us to be well assured on this vital point, for to be unregenerated is to be unsaved, unpardoned, without God, and without hope."

~ Charles Spurgeon (paraphrased)