Origen — as excerpted in the Catena Aurea on Matthew 26:6-13

“Oil is throughout Scripture put for the work of mercy, with which the lamp of the word is fed; or for doctrine, the hearing of which sustains the word of faith when once kindled. All with which men anoint is comprehensively called oil; and one kind of oil is unguent, and one kind of unguent is precious. So all righteous acts are called good works; and of good works there is one kind which we do for, or to, men; another which we do for, or to, God. And this likewise that we do for God, in part only advances the good of men, in part, the glory of God. For example, one does a kindness to a man out of feelings of natural righteousness, not for God’s sake, as the Gentiles sometime did; such a work is common oil of no fine savour, yet is it acceptable to God, forasmuch, as Peter says in Clement, the good works that the unbelievers do, profit them in this world, but avail not to gain them eternal life in another. They who do the same for God’s sake, profit thereby not in this world only but in the next also, and that they do is ointment of good savour. Another sort is that done for the good of men, as alms, and the like. He who does this to Christians, anoints the Lord’s feet, for they are the Lord’s feet; and this penitents are most found to do for remission of their sins. He who devotes himself to chastity, and continues in fastings and prayers, and other things which conduce to God’s glory only, this is the ointment which anoints the Lord’s head, and with whose odour the whole Church is filled; this is the work meet not for penitents, but for the perfect, or the doctrine which is necessary for men; but the acknowledgment of the faith which belongs to God alone, is the ointment with which the head of Christ is anointed, with which we are buried together with Christ by baptism into death. (Rom. 6:4.)”