Ps 39:1

“Let us say then what this Psalm says. "I waited patiently for the Lord" [Psalm 40:1]. I waited patiently for the promise of no mere mortal who can both deceive and be himself deceived: I waited for the consolation of no mere mortal, who may be consumed by sorrow of his own, before he gives me comfort. Should a brother mortal attempt to comfort me, when he himself is in sorrow likewise? Let us mourn in company; let us weep together, let us "wait patiently" together, let us join our prayers together also. Whom did I wait for but for the Lord? The Lord, who though He puts off the fulfilment of His promises, yet never recalls them? He will make it good; assuredly He will make it good, because He has made many of His promises good already: and of God's truth we ought to have no fears, even if as yet He had made none of them good. Lo! let us henceforth think thus, "He has promised us everything; He has not as yet given us possession of anything; He is a sponsible Promiser; a faithful Paymaster: do you but show yourself a dutiful exactor of what is promised; and if you be "weak," if you be one of the little ones, claim the promise of His mercy. Do you not see tender lambs striking their dams' teats with their heads, in order that they may get their fill of milk? ..."And He took heed unto me, and heard my cry." He took heed to it, and He heard it. See thou hast not waited in vain. His eyes are over thee. His ears turned towards thee. For, "the eyes of the Lord are upon the righteous, and His ears are open unto their cry." What then? Did He not see thee, when thou usedst to do evil and to blaspheme Him? What then becomes of what is said in that very Psalm, "The face of the Lord is upon them that do evil"? But for what end? "that He may cut off the remembrance of them from the earth." Therefore, even when thou wert wicked, He "took heed of thee;" but He "took no heed to thee." So then to him who "waited patiently for the Lord," it was not enough to say, "He took heed of me," He says, "He took heed to me;" that is, He took heed by comforting me, that He might do me good. What was it that He took heed to? "and He heard my cry."”

“In the preceding Psalms, the Psalmist invoked divine help against the malice of the wicked and showed the purpose of his caution; here, however, he treats of confidence in divine help. And concerning this he does two things. First, he describes this confidence itself. Second, he treats of the mercy that is the cause of confidence, at Ps. 40: "Blessed is he who understands." Concerning the first he does two things. First, he commemorates the confidence he has in God, continuing from past events. Second, by seeking future things, at "But you, O Lord." Concerning the first he does two things. First, he commemorates the confidence he has in God by recounting past benefits. Second, he shows the mercy of God through which he bestows benefits, at "You have done many things." This Psalm mystically treats of the change from the old covenant to the new. The title: "Unto the end, a Psalm of David." In other Psalms, the "end" is taken as referring to Christ. Rom. 10: "Christ is the end of the law." Here the "end" is taken as the new covenant, which is the end of the old. 1 Tim. 1: "The end of the commandment is charity." Concerning the first part, he commemorates three things. First, the efficacy of confidence in general. Second, he touches upon it in particular, at "He set." Third, he shows this to be present in others, at "Many shall see." Concerning the first he does two things. First, he touches upon the confidence, showing it to be efficacious. Second, the sign of confidence. He says therefore, "Waiting, I waited." This text is understood as meaning that David, in his own person, many times waited for divine help. But because he speaks in the person of the Church, it is better that it be understood as referring to the human race awaiting the grace of the new covenant. And he says, "Waiting, I waited for the Lord," to show continuity: because although he delayed, yet he did not fail: Hab. 2: "If he delays, wait for him, for he will surely come." And thus every just person ought always to remain in confidence in God, because he does not fail those who hope in him. Or it refers to the various states of those who waited: because the patriarchs and prophets and all others waited, as is commonly held. To the outward waiting he adds intention, when he says, "And he attended to me": because although God hears all, yet he does not attend to all, because not all are ordered to the good; and therefore, "He attended to me," that is, for my benefit. The sign of confidence is supplication: because no one finally asks unless he hopes to be heard. And therefore he says, "And he heard my prayers": Ps. 142: "He regarded the prayer of the humble, and he brought me out of the pit of misery."”