Psalm 26 is a chiastic text:

A. I have walked with integrity and truth, vv 1-3 (Yahweh 3x)

B. I don’t sit with the deceifful or wicked, vv 4-5

C. I wash in innocence, process around the altar, love Yahweh’s house, vv 6-8 (Yahweh 2x)

B’. Do not take me away with wicked, vv 9-10

A’. I walk with integrity and my food is firm, vv 11-12 (Yahweh 1x)

David’s washing, procession at the altar, thanksgiving, and love for God distinguishes him from the wicked. When Yahweh takes the souls of the wicked, He will not take the soul of David.

A scene of worship stands at the center of the Psalm, but that’s already in play at the beginning. David asks for vindication (shafat), suggesting a judicial setting, but the inspection that he asks for goes beyond anything a court might do: He wants Yahweh to examine (bachan) the inner man, the kidneys (kilyot) and heart (leb). 

This is a pre-sacrificial inspection, as when a priest checks for blemishes in a sacrificial animal. But this inspection goes beyond anything that a priest could perform; to inspect the kidneys and heart, a priest has to open the animal. For human priests, inspection of internal organs takes place after the sacrifice. 

Yahweh, a divine priest, a divine haruspex, with his burning eyes, sees through flesh to the inner man beforehand.