The Enchiridion by St. Augustine
Chapter 117.--Love, Which is Greater Than Faith and Hope, is Shed Abroad in Our Hearts by the Holy Ghost.
And now as to love, which the apostle declares to be greater than the other two graces, that is, than faith and hope, the greater the measure in which it dwells in a man, the better is the man in whom it dwells. For when there is a question as to whether a man is good, one does not ask what he believes, or what he hopes, but what he loves. For the man who loves aright no doubt believes and hopes aright; whereas the man who has not love believes in vain, even though his beliefs are true; and hopes in vain, even though the objects of his hope are a real part of true happiness; unless, indeed, he believes and hopes for this, that he may obtain by prayer the blessing of love. For, although it is not possible to hope without love, it may yet happen that a man does not love that which is necessary to the attainment of his hope; as, for example, if he hopes for eternal life (and who is there that does not desire this?) and yet does not love righteousness, without which no one can attain to eternal life. Now this is the true faith of Christ which the apostle speaks of, |which worketh by love;| and if there is anything that it does not yet embrace in its love, asks that it may receive, seeks that it may find, and knocks that it may be opened unto it. For faith obtains through prayer that which the law commands. For without the gift of God, that is, without the Holy Spirit, through whom love is shed abroad in our hearts, the law can command, but it cannot assist; and, moreover, it makes a man a transgressor, for he can no longer excuse himself on the plea of ignorance. Now carnal lust reigns where there is not the love of God.