In fact, the love that a man has for others arises in man from the love that he has for himself, for a man stands in relation to a friend as he does to himself. But a person loves himself inasmuch as he wishes the good for himself, just as he loves another person by wishing him good. So, by the fact that a man is interested in his own good he is led to develop an interest in another person’s good. Hence, because a person hopes for good from some other person, a way develops for man to love that other person in himself, from whom he hopes to attain the good. Indeed, a person is loved in himself when the lover wishes the good for him, even if the lover may receive nothing from him. Now, since by sanctifying grace there is produced in man an act of loving God for Himself,the result was that man obtained hope from God by means of grace. However, though it is not for one’s own benefit, friendship, whereby one loves another for himself, has of course many resulting benefits, in the sense that one friend helps another as he helps himself. Hence, when one person loves another, and knows that he is loved by that other, he must get hope from him. Now, by grace man is so established as a lover of God, through the love of charity, that he is also instructed by faith that he is first loved by God: according to the passage found in 1 John (4:10): “In this is charity: not as though we had loved God, but because He hath first loved us.” It follows, then, from the gift of grace that man gets hope from God. It is also clear from this that just as hope is a preparation of man for the true love of God, so also man is conversely strengthened in hope by charity.
Summa contra Gentiles III.153.2