Psalms 17:3

David was not asking for acceptance by God because of his own righteousness. He claimed that in the present conflict, in which evil people were opposing him, he had done nothing worthy of their antagonism. God had examined David’s attitudes, as well as his actions, and had no basis for condemning him. Furthermore, David had previously made a strong commitment not to sin.

". . . he requests God to ’test’ his ’heart’ (see Psalms 7:9), i.e., to put him through every conceivable examination. The probing (bahan, see Psalms 7:9) of ’the heart’ (Psalms 17:3 a) is a determination of the purity and integrity of the heart. Even as silver and gold underwent a refining process and were tested until the smith was satisfied with the purity of these precious metals, so the psalmist asks for an examination of his purity of devotion to God." [Note: VanGemeren, p. 162.]