Charles H. Spurgeon on Psalms 139:23

Try me. True faith is precious; it is like gold, it will endure a trial. Presumption is but a counterfeit, and cannot abide to be tried: 1Pe 1:7. A true believer fears no trial. He is willing to be tried by God. He is willing to have his faith tried by others, he shuns not the touchstone. He is much in testing himself. He would not take anything upon trust, especially that which is of such moment. He is willing to hear the worst as well as the best. That preaching pleases him best which is most searching and distinguishing: Heb 4:12. He is loath to be deluded with vain hopes. He would not be flattered into a false conceit of his spiritual state. When trials are offered, he complies with the apostle's advice, 2Co 13:5. —David Clarkson.