O Lord, open Thou my lips; and my mouth shall shew forth Thy praise. -Psalm 51:15

Prayer and praise are like the two cherubim on the ark, they must never be separated. In the model of prayer which our Saviour has given us, saying, “After this manner pray ye,” the opening part of it is rather praise than prayer-“Our Father which art in heaven, hallowed be Thy name,” and the closing part of it is praise, where we say, “For Thine is the kingdom, the power, and the glory, for ever and ever. Amen.” David, who is the great tutor and exemplar of the church as to her worship, being at once her poet and her preacher, takes care in almost every psalm, though the petition may be agonizing, to mingle exquisite praise. Take for instance, that psalm of his after his great sin with Bathsheba. There one would think, with sighs and groans and tears so multiplied, he might have almost forgotten or have feared to offer thanksgiving while he was trembling under a sense of wrath; and yet ere the psalm that begins “Have mercy upon me, O God,” can come to a conclusion the psalmist has said: “O Lord, open Thou my lips, and my mouth shall show forth Thy praise,” and he cannot pen the last word without beseeching the Lord to build the walls of Jerusalem, adding the promise, “then shalt Thou be pleased with the sacrifices of righteousness, with burnt offering and whole burnt offering: then shalt they offer bullocks upon Thine altar.” I need not stop to quote other instances, but it is almost always the case that David by the fire of prayer warms himself into praise. He begins low, with many a broken note of complaining, but he mounts and glows, and, like the lark, sings as he ascends.~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1469.cfm