O blessed are they which love you, for they shall rejoice in your peace: blessed are they which have been sorrowful for all your scourges; for they shall rejoice for you, when they have seen all your glory, and shall be glad for ever.
Read Chapter 13
Augustine of Hippo
AD 430
Everything is loved among friends, and it is so loved that the human conscience feels guilty before itself if it does not love one who returns the love and if it does not give love for love, seeking nothing in a bodily way beyond the signs of good will. From this comes that lamentation, if someone dies, the darkness of sorrow and the heart steeped in tears, by sweetness turned to bitterness, and the death of the living arising from the lost life of the dead. Happy is one who loves God and his friend in God and his enemy because of God. He alone loses no dear one, since all people are dear in God who is never lost. And who is this but our God, the God who is the maker of heaven and earth and who fills them up because he makes them by filling them? No one loses God unless he leaves God. And, because he leaves God, where can he go or flee except from your pleasure into your ire? For where does he not find your law in his punishment? And “your law is the truth” and “you are the truth.” - "Confessions 4.9.14"
