8 You heard what was read today: The Saviour ordered that the foal of an ass should be brought to Him by the apostles, and bade them say, if any one withstood them: “The Lord has need of him.” What if now, too, He has commanded that foal of an ass, that is, the foal of that animal which is wont to bear a heavy burden, as man must, to whom is said: “Come unto Me all you that labour and are heavy laden, and I will give you rest; take My yoke upon you, for it is easy;” what if, I say, He has commanded that foal to be brought to Him now, sending forth those apostles, who, having put off their body, wear the semblance of the angels unseen by our eyes?
If withstood by any, will they not say: The Lord has need of him? If, for instance, love of this life, or flesh and blood, or earthly intercourse (for perhaps we seem pleasing to some), were to withstand them? But he who loves me here, would show his love much more if he would suffer me to become Christ's victim, for “to depart and be with Christ is much better, though to abide in the flesh is more needful for you.” There is nothing therefore for you to fear, beloved brethren. For I know that whatever I may suffer, I shall suffer for Christ's sake. And I have read that I ought not to fear those that can kill the flesh. And I have heard One Who says: “He that loses his life for My sake shall find it.”
Source: Sermon against Auxentius (New Advent)