26 Wherefore, O Emperor, that I may now address my words not only about you, but to you, since you observe how severely the Lord is wont to censure, see that the more glorious you have become, the more utterly you submit to your Maker. For it is written: “When the Lord your God shall have brought you into a strange land, and you shall eat the fruits of others, say not, My power and my righteousness has given me this, for the Lord your God has given it to you;” for Christ in His mercy has conferred it on you, and therefore, in love for His body, that is, the Church, give water for His feet, kiss His feet, so that you may not only pardon those who have been taken in sin, but also by your peaceableness restore them to concord, and give them rest.
Pour ointment upon His feet that the whole house in which Christ sits may be filled with your ointment, and all that sit with Him may rejoice in your fragrance, that is, honour the lowest, so that the angels may rejoice in their forgiveness, as over one sinner that repents, the apostles may be glad, the prophets be filled with delight. For the eyes cannot say to the hand: “We have no need of you, nor the head to the feet, You are not necessary to me.” So, since all are necessary, guard the whole body of the Lord Jesus, that He also by His heavenly condescension may preserve your kingdom.
Source: Letters (New Advent)