Ps 103:34

“Thus then, being before instructed and taught, they [the people of Israel] learned not to do service to any one but the Lord. They began to know how long the shadow would last and not to forget the time that was at hand, in which no longer should the bullock of the herd be a sacrifice to God, or the ram of the flock or the he-goat, but all these things should be fulfilled in a purely spiritual manner and by constant prayer and upright conversation, with godly words; as David sings, "May my meditation be pleasing to him. Let my prayer be set forth before you as incense, and the lifting up of my hands as the evening sacrifice." The Spirit also, who is in him, commands, saying, "Offer to God the sacrifice of praise, and pay to the Lord your vows. Offer the sacrifice of righteousness, and put your trust in the Lord."”

“Prayer is a great good: someone conversing with a virtuous person gains no little advantage from the experience, so how much good will the one communing with God be granted? Prayer, after all, is conversing with God. For proof of this, listen to the words of the inspired author: "Let my meditation be pleasing to God," that is, may my words seem acceptable to God. I mean, he is able to offer help before we ask for it, isn't he? Still, he wants so as to take occasion from us for daily bestowing on us providential care from himself. Accordingly, whether we have our requests granted or not, let us persist in asking, and render thanks not only when we gain what we ask but also when we do not. Failure to gain, you see, when that is what God wants, is not worse than succeeding; we do not know what is to our advantage in this regard in the way he does understand. The result is, then, that succeeding or failing we ought to give thanks.”

“"Let my discourse be pleasing to Him: my joy shall be in the Lord." What is the discourse of man unto God, save the confession of sins? Confess unto God what thou art, and thou hast discoursed with Him. Discourse unto Him, do good works, and discourse. "Wash you, make you clean," saith Isaiah. What is it to discourse unto God? Unfold thyself to him who knoweth thee, that He may unfold Himself to thee who knowest not Him. Behold, it is thy discourse that pleaseth the Lord; the offering of thy humility, the tribulation of thy heart, the holocaust of thy life, this pleaseth God. But what is pleasing to thyself? "My joy shall be in the Lord." This is that discoursing which I meant between God and thyself: show thyself to Him who knoweth thee, and He showeth Himself unto thee who knowest not him. Pleasing unto Him is thy confession: sweet unto thee is His grace. He hath Spoken Himself unto thee. How? By the Word. What Word? Christ. ...”

“For all creatures declare God. What shall I do? I shall sing with them all. The thick cord in the zither does not give forth a pleasant sound if struck alone, but there is harmony in consonance with others. So does the man who sees God in all things, who tastes God in them through his three powers. "Pleasing to Him be my theme; I will be glad in the Lord." And elsewhere: "For you make me glad, O Lord, by Your deeds." Again: "I will glorify Him with thanksgiving." In all things there is taste and restoration for the intellective and the affective powers.”