“. . . as a crown, so let us bear about the cross of Christ. Yea, for by it all things are wrought, that are wrought among us. Whether one is to be new-born, the cross is there; or to be nourished with that mystical food, or to be ordained, or to do anything else, everywhere our symbol of victory is present. Therefore both on house, and walls, and windows, and upon our forehead, and upon our mind, we inscribe it with much care.
For of the salvation wrought for us, and of our common freedom, and of the goodness of our Lord, this is the sign. For as a sheep was He led to the slaughter (Isaiah 53:7). When therefore you sign yourself, think of the purpose of the cross, and quench anger, and all the other passions. When you sign yourself, fill your forehead with all courage, make your soul free.
…This therefore do thou engrave upon your mind, and embrace the salvation of our souls. For this cross saved and converted the world, drove away error, brought back truth, made earth Heaven, fashioned men into angels. Because of this, the devils are no longer terrible, but contemptible; neither is death, death, but a sleep; because of this, all that wars against us is cast to the ground, and trodden under foot.
(St. John Chrysostom, Let Us Attend, p. 54 & 55)