Psalm 26 is an interesting Psalm in the sense that the Psalmist actually requests for God to examine him, to test him, to try him in order to see and discern whether or not his integrity is genuine and right before God. The Psalmist, which is David, is displaying his heart for sanctification and holiness. He longs to be separated from sin and ‘pretenders’/worthless men. He not only desires to be separated from all this, but set apart to God through holiness.
The one who actually desires to be examined, tested and tried by God definitely displays this kind of passion for true biblical piety. And so David offers himself on the alter of examination, which gives good evidence of one who is genuinely devoted to God.
We are commanded by God through Paul to do this as well. Paul tells the Corinthians to ‘test and examine yourselves to see if you are in the faith’. And what is interesting with David is he is requesting for God to examine him. So we see this as a good biblical practice for all the saints. For from this will bring one of two things:
(1) An assurance of God’s saving and sustaining grace on the Christian.
(2) Or an assurance that one is not in the faith.
For the Christian, this is the beginning of true piety to God. For the one who finds themselves 'not in the faith' this could be the beginning of a beautiful work of regeneration, whereby God is making all things new!