Psalms 51:4

Against thee, thee only... — This can refer to nothing but a breach of the covenant-relation by the nation at large. An individual would have felt his guilt against the nation or other individuals, as well as against Jehovah. The fact that St. Paul quotes (from the LXX.) part of the verse in Romans 3:4 (see Note, New Testament Commentary) has naturally opened up an avenue for discussion on the bearing of the words on the doctrines of free-will and predestination. But the immediate object of his quotation appears to be to contrast the faithfulness of the God of the covenant with the falsehood of the covenant people (“Let God be true, and every man a liar”). The honour of God, as God of the covenant, was at stake. It is this thought which appears in the last clauses of this verse.

That... — So that (or, in order that) thou art (or mayest be) justified in thy cause, and clear in thy judgment. The Hebrew, rendered in the Authorised Version when thou speakest, is often used of a cause or suit (see (Exodus 18:16, “matter,” &c), and it is here plainly used in this sense and is parallel to judgment. The clause seems to imply not only a sense of a breach of the covenant, but some manifest judgment from Jehovah in consequence; and, as usual, it is of its effect on the heathen that the psalmist thinks. The Divine honour would be justified when the suffering nation confessed that condemnation and punishment had been deserved. This was apparently the meaning read in the words by the LXX.