Thomas Aquinas, on Ps 18:8

“The law of the Lord is unspotted, converting souls: the testimony of the Lord is faithful, giving wisdom to little ones.”

“"The justices of the Lord are right," that is, those judgments that are spoken of in Ex. 22: "He who has stolen an ox or a sheep," and so on. Is. 26: "The path of the just is straight for walking": Prov. 21: "It is joy for the just man to do justice, and dread for those who work iniquity." And he says two things about them: that they are right, and that they are joyful. Right, because they contain justice. What is right is called just: Prov. 8: "All my words are just, and there is nothing wicked or perverse in them; they are right to those who understand," and so on. Joyful, not harsh and disturbing, because they are mixed with equity; hence he says, "Rejoicing hearts," because of the equity and the hope of reward: Ps. 118: "I shall rejoice in your words." But the moral precepts are bright and illuminating; hence he says, "The commandment of the Lord is bright." It is called bright because it is manifest and evident in itself, as here: "You shall not kill," "You shall not commit adultery," "You shall not steal," and similar things, which have clarity in themselves, that everyone is bound to observe, as Prov. 6 says: "The commandment is a lamp, and the law is a light." A precept is called that to which attention is directed according to the command of a superior; and it concerns things to be done, and imports a duty of acting in the one to whom it is commanded. This duty arises either from the divine rule which we are bound to follow -- and thus that falls under obligation without which the order of reason cannot be preserved; or it is a duty from the authority of the one commanding, whom we are bound to obey; or from the end, which we entirely desire, which is appointed for us -- and then that falls under precept without which we cannot maintain subjection to the one commanding, or without which we cannot attain the intended end. For a precept is so called as though "precisely taken," namely for acting -- as though we are precisely bound to do that. And therefore such a precept is "enlightening the eyes," namely of reason, which eyes are darkened by the desire for exterior things and the interior passions of concupiscence; and the precept of the Lord removes this, and therefore it is "enlightening the eyes." "Enlighten my eyes, lest I ever sleep in death," Ps. 12.”

Imported from an open dataset — not yet checked against the printed edition.