Gregory of Nyssa

A man, then, who remains the same and yet prattles to himself about the change for the better that 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 yet become. The Gospel says of the regenerate, however, 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 have 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 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.” “The Lord is kind to all and is not angry with us every day.” “God is straightforward, and there is no unrighteousness in him.” This is what fathers do for children. Similar sayings are 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.