Chapter 28 — Part III: The Decalogue — The Fifth Commandment
Section 2. The necessity of explaining this Commandment is proved from the following. Immediately after the earth was overwhelmed in universal deluge, this was the first prohibition made by God to man. I will require the blood of your lives, He said, at the hand of every beast and at the hand of man. In the next place, among the precepts of the Old Law expounded by our Lord, this Commandment was mentioned first by Him; concerning which it is written in the Gospel of St. Matthew: It has been said thou shalt not kill, etc.