在福音中，耶穌教門徒如何能更相稱地跟隨祂: 「我給你們一條新命令：你們該彼此相愛。」但舊的法律不是說要「愛人如己」(肋未紀 19:18)? 那麼祂為何叫這誡命做新命令? 分別在於愛。耶穌指出這種愛跟世俗的愛不同: 「如同我愛了你們，你們也該照樣彼此相愛。」不是出於人的愛，而是作為至高天主子女，由於跟祂的獨生子如兄弟般接近，而因此可以像祂愛世人那般彼此相愛。他們也因此而滿足。
但不要以為另一條誡命: 「我們應愛天主」就不再需要遵守。如果我們明白這兩條誡命，就知道它們是相輔相成的。一個愛天主的人不可能憎惡祂要我們愛人這誡命；一個極愛鄰人的人也必定愛天主。當耶穌說「如同我愛了你們」，就是指這種愛與出於人的愛完全不同。祂愛我們，就是愛在我們內的天主；祂不介意我們是誰，卻只想我們因此變得肖似祂? 讓我們彼此相愛，由此我們互相成為天主的居所。
In the Gospel, Jesus teaches them how to make themselves fit to follow Him: A new commandment I give to you, that you love one another. But does not the old law say, you shall love your neighbor as yourself (Lev 19:18)? Why then does He call it a new commandment? The difference is Love. Love does do this; but it is that love which our Lord distinguishes from worldly love: As I have loved you, that you also love one another. Not the love with which men love one another, but that of the children of the Most High God, who would be brethren of His only-begotten Son, and therefore love one another with that love with which He loved them, and would lead them to the fulfillment of their desires.
But; do not think that that greater commandment, that we: should love the Lord our God, is passed by. If we understand the two precepts, each is implied in the other. He who loves God cannot despise His commandment that he should love his neighbor; and he who loves his neighbor in a heavenly spiritual way, loves God. That is the love which our Lord distinguishes from all human love, when He adds, As I have loved you. What did He, in loving us, love, but God in us; not who was in us, but so that He might be? Wherefore let each of us so love the other, as that by this working of love, we make each other the habitations of God.