15 For this is to change what you had been, and to begin to be what you were not, that the divine birth might shine forth in you, that the godly discipline might respond to God, the Father, that in the honour and praise of living, God may be glorified in man; as He Himself exhorts, and warns, and promises to those who glorify Him a reward in their turn, saying, “Them that glorify me I will glorify, and he who despises me shall be despised.” For which glorification the Lord, forming and preparing us, and the Son of God instilling the likeness of God the Father, says in His Gospel: “You have heard that it has been said, You shall love your neighbour, and hate your enemy.
But I say unto you, Love your enemies, and pray for them which persecute you; that you may be the children of your Father which is in heaven, who makes His sun to rise on the good and on the evil, and sends rain upon the just and on the unjust.” If it is a source of joy and glory to men to have children like to themselves— and it is more agreeable to have begotten an offspring then when the remaining progeny responds to the parent with like lineaments— how much greater is the gladness in God the Father, when any one is so spiritually born that in his acts and praises the divine eminence of race is announced!
What a palm of righteousness is it, what a crown to be such a one as that the Lord should not say of you, “I have begotten and brought up children, but they have despised me!” Let Christ rather applaud you, and invite you to the reward, saying, “Come, you blessed of my Father, receive the kingdom which is prepared for you from the beginning of the world.”
Source: The Treatises of Cyprian (New Advent)