For the Scripture saith, “And Abraham circumcised ten, and eight, and three hundred men of his household.” What, then, was the knowledge given to him in this? Learn the eighteen first, and then the three hundred. The ten and the eight are thus denoted—Ten by Ι, and Eight by Η. You have the initials of the, name of Jesus. And because the cross was to express the grace of our redemption by the letter Τ, he says also, “Three Hundred.” He signifies, therefore, Jesus by two letters, and the cross by one.
Epistle of Barnabus
Chapter IX