John Calvin Commentary Psalms 51:14

"Deliver me from bloodguiltiness, O God, thou God of my salvation; [And] my tongue shall sing aloud of thy righteousness." — Psalms 51:14 (ASV)

Deliver me from bloods. His frequent return to petitions for pardon proves how far David was from flattering himself with unfounded hopes, and what a severe struggle he sustained with inward terrors. According to some, he prays in this verse to be delivered from the guilt of the blood of Uriah, and, in general, of the whole army.

But the term bloods in Hebrew may denote any capital crime, and, in my opinion, he is here to be considered as alluding to the sentence of death, to which he felt himself liable, and from which he requests deliverance. By the righteousness of God, which he pledges to celebrate, we are to understand His goodness; for this attribute, as usually ascribed to God in the Scriptures, does not so much denote the strictness with which He exacts vengeance, as His faithfulness in fulfilling the promises and extending help to all who seek Him in the hour of need.

There is much emphasis and vehemence in his manner of address, O God! the God of my salvation, intimating at once how acutely he sensed the danger of his situation, and how strongly his faith rested upon God as the ground of his hope. Similar is the tenor of the verse which follows.

He prays that his lips may be opened; in other words, that God would provide him with cause for praise. The meaning usually attached to the expression is that God would so direct his tongue by the Spirit as to enable him to sing His praises.

But though it is true that God must supply us with words, and that if He does not, we cannot fail to be silent in His praise, David seems rather to suggest that his mouth must be shut until God called him to the exercise of thanksgiving by extending pardon. In another place, we find him declaring that a new song had been put in his mouth (Psalms 40:3), and it seems to be in this sense that he here desires his lips to be opened.

He again signifies the gratitude which he would feel, and which he would express, intimating that he sought the mercy of God with no other purpose than that he might become the herald of it to others. My mouth, he says emphatically, shall show forth Your praise.