This question is only that which is a problem common to all skilled in the law, namely, that the commandments are differently set forth in Exodus, Leviticus, and Deuteronomy. Wherefore He brought forward not one but two commandments, by which, as by two paps rising on the breast of the bride, our infancy is nourished.
And therefore there is added, “And Jesus answered him, The first of all the commandments is, Hear, O Israel; the Lord thy God is one God.” He mentions the first and greatest commandment of all; this is that to which each of us must give the first place in his heart, as the only foundation of piety, that is, the knowledge and confession of the Divine Unity, with the practice of good works, which is perfected in the love of God and our neighbour.
Wherefore there is added, “Thou shalt love the Lord thy God with all thy heart, and with all thy mind, and with all thy soul, and with all thy strength: this is the first commandment.”
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).