The psalmist confesses his sin to God: I know my transgressions; know here has the sense of admitting or confessing to oneself; transgressions translates the same word used in verse 1b, and sin the word used in verse 2b. The expression is before me in verse 3b means “I am conscious of,” “I am aware of,” parallel with I know in verse 3a. The psalmist intends to confess all his sins; he will not hide anything. In languages which use a verb phrase for my sin, it will often be necessary to say, for example, “I know that I do evil deeds.”
He confesses that his sin was against God: Against thee, thee only is what he says. Some (see Taylor) point out that it would be difficult for David to have said that, since his sin was against Uriah, Bathsheba’s husband, and against Bathsheba as well. But the ardor of the psalmist’s confession and his recognition that sin is primarily an offense against God are not the criteria for deciding the historical question of authorship. And it should be noted that David, when confronted with the denunciation of his adultery with Bathsheba and his murder of her husband Uriah, confessed: “I have sinned against the LORD” (2 Sam 12.13). In some languages it is not possible to say that one has sinned against someone. To sin against is sometimes rendered “to sin in your eyes;” for example, “I have sinned in your eyes–only in your eyes.” It is also possible to say, for example, “I have sinned and offended you.”
In thy sentence (verse 4c) translates what is literally “in your speaking,” that is, in your pronouncing the sentence of “Guilty!” Some Hebrew manuscripts have “in your words,” which Briggs prefers and interprets as a reference to the Ten Commandments. In thy judgment in line d is parallel with in thy sentence in line c. Thou art justified in line c means that God does the right thing; he is not guilty of injustice in condemning the psalmist. The same thought is repeated in line d, and blameless, that is, God is not at fault; rather he is innocent of injustice or wrongdoing in his ruling.
Thou art justified in thy sentence may in some languages be rendered “you are right when you say that I am guilty” or, in direct discourse, “you are right when you say to me, ‘You are guilty.’ ” The expression blameless in thy judgment can sometimes be translated as “you are fair when you say that I am guilty” or “you judge me fairly when you condemn me.”
In Romans 3.4 Paul quotes the second half of verse 4 as translated by the Septuagint, with a meaning quite different from that of the Hebrew text.
Quoted with permission from Bratcher, Robert G. and Reyburn, William D. A Handbook on the Book of Psalms. (UBS Helps for Translators). New York: UBS, 1991. For this and other handbooks for translators see here .