Gregory of Nyssa

A person, then, who remains the same and yet babbles to himself about the change for the better he has undergone in baptism should attend to what Paul says: "If anyone thinks he is something when he is nothing, he deceives himself." For you are not what you have not become; whereas the gospel says of the regenerate that "he gave all those who received him the power to become God's children." Now the child born of someone certainly shares his parent's nature. If, then, you have received God and become his child, let your way of life testify to the God within you; make it clear who your Father is! The marks by which we recognize God are the very ones by which a son of his must show his relation to him: "he opens his hand and fills everything living with joy"; "he overlooks iniquity"; "he relents of his evil purpose";29 "the Lord is kind to all and is not angry with us every day"; "God is straightforward, and there is no unrighteousness in him"31—and the similar sayings scattered through Scripture for our instruction. If you are like this, you have genuinely become a child of God. But if you persist in displaying the marks of evil, it is useless to babble to yourself about the birth from above. Prophecy will tell you, "You are a son of humankind, not a son of the most High. You love vanity and seek lies. You fail to realize that the only way one is magnified is by becoming holy."