EXPOSITION
HERE we have again a psalm without a title, and, so far, we are left to conjecture its age and author. The Jews, however, have always regarded it as Davidical; and there is evidence in Scripture itself (Acts 4:25) that the early Christians were of the same opinion. Modern critics, for the most part, agree, although there are some (Ewald, Paulus, Bleek) who ascribe it to Solomon, and others (Maurer, Delitzsch) who suppose it written by Hezekiah or Isaiah.
The psalm is certainly Messianic. It is assumed to be so in Acts 4:25; Acts 13:33; Hebrews 1:5; Hebrews 5:5. However it may, to a certain extent, apply to David, David cannot exhaust its allusions. Hebrews 5:7, Hebrews 5:8, and Hebrews 5:12 are inapplicable to David, and must refer to the Messiah. The Jews admitted the Messianic character of the psalm, until driven into denial by the controversy with Christians. Most modern critics allow it.
There is a certain correspondency between Psalms 1:1-6. and 1; which may account for their being placed together. In beth the main idea is the antagonism between the righteous and the wicked. Isaiah sets forth this antagonism by a contrast between two typical individuals. Psalms 51:1-19 shows the two kingdoms of light and darkness engaged in their internecine conflict.