Glossa Ordinaria

And the law of life. The natural law, which he gave to every man, that he might be subject to his creator and might guard within himself the honorableness of good works. Or, the law of the letter, which he willed to be written for the correction of morals and the restoration of the natural law; for this is what the natural and the literal law implies, that we love God with the whole heart, the whole soul, the whole strength: and that we keep his commandments in the love of God and of neighbor.