And this takes place, as we have already intimated, not accidentally, but by an immutable law. Eternal law is at the bottom; and, therefore, eternal truth is in it. It is the law of men, the law of angels; and we might add, with the simple modification that what is faith in the human mind becomes knowledge in the divine mind, that it is the law of God. God loves, and he can love, only what he knows to be a proper object of love. In men, who are not the subjects of absolute knowledge, faith takes the place of such knowledge; and they love, and can love, only as they believe. “Believe,” says Archbishop Leighton, “and you shall love. Believe much, and you shall love much.” And carrying out the principle to its legitimate issues, I think we may add with safety, Believe with all your powers of belief, and you will love with all your powers of love. Believe with assurance of faith, and you will love with assurance of love. In other words, believe perfectly, and you will love perfectly.
— The Life of Faith (1852) Part 1, Chapter 6.