20 But the Church has oil wherewith she dresses the wounds of her children, lest the hardness of the wound spread deeply; she has oil which she has received secretly. With this oil Asher washed his feet as it is written: “A blessed son is Asher, and he shall be acceptable to his brothers, and shall dip his feet in oil.” With this oil, then, the Church anoints the necks of her children, that they may take up the yoke of Christ; with this oil she anointed the Martyrs, that she might cleanse them from the dust of this world; with this oil she anointed the Confessors, that they might not yield to their labours, nor sink down through weariness; that they might not be overcome by the heat of this world; and she anointed them in order to refresh them with the spiritual oil.
Source: Letters (New Advent)