Thomas Aquinas, on Ps 39:2

“With expectation I have waited for the Lord, and he was attentive to me.”

“Here he presents in particular the efficacy of confidence in the things in which he was heard. And he touches upon three things. First, deliverance from evils. Second, the bestowal of goods, at "And he set." Third, thanksgiving for both, at "And he put." Now there is a twofold evil from which men flee: namely the evil of misery and of punishment. As to the first he says, "He brought me out of the pit of misery." And this can also refer to the temporal misery in which David once found himself. And the temporal misery is called a pit because of its depth and multiplicity. It can also refer to the misery of guilt: because "sin makes peoples miserable," Prov. 14. And both can be reduced to the guilt of carnal vices, when he says, "from the pit of misery," that is, from the depth of carnal sins. Or it can refer to spiritual sins, by which a just person is entangled in sins; hence he says, "from the mire of the dregs." Referring to carnal sins, he does not say "mire" simply, but "of the dregs," or "of dung" according to Jerome, because mire in uncorrupted earth is not sediment, nor is it foul and abominable. Or, "the pit of misery," that is, hell, from which the saints were led out by Christ. And the mire is the reproach from which the saints were led out, in which they were held by the demons. Next he treats of the bestowal of goods, in which he presents two praiseworthy things. First, that a person be established in good things; and with regard to this he says, "He set my feet upon a rock," that is, my affections by which I must proceed on the spiritual way. The rock is called the foundation of divine help: 2 Sam. 22: "The Lord is my rock." Or the rock is called Christ: 1 Cor. 10: "And the rock was Christ." And thus he established me upon the rock, that is, upon divine help. Or upon Christ, "my feet," that is, my affections. The second is that one advance in good things; and with regard to this he says, "And he directed my steps," that is, he guided me toward better things: Prov. 16: "The heart of a man plans his way, but it is the Lord who directs his steps."”

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