Oh let the wickedness of the wicked come to an end; but establish the just: for the righteous God trieth the hearts and reins.
Oh let the wickedness ... come to an end. This prayer is granted in the prophetical view of the Psalmist (Psalms 10:6), "O thou enemy, destructions are come to a perpetual end."
The wicked ... the just - represented respectively by Saul and David. It was not a mere contest between them as individuals, but between the universal and everlasting principles of wickedness and righteousness. In Saul's overthrow by God's judicial interposition and David's elevation, un-godliness would receive a deadly blow, and righteousness a material vindication. There may be an allusion designed by the Spirit to David's anti-type, "the just one," Messiah; because the Hebrew is singular, not plural.
For the righteous God trieth the hearts - which ensures thy putting an end to the wicked and establishing For the righteous God trieth the hearts - which ensures thy putting an end to the wicked and establishing the just (Jeremiah 17:10; Jeremiah 20:12).
Reins - literally, the kidneys, the most hidden part of the body, often affected by the working of the mind.