Adam Clarke on Psalms 7:15

He made a pit - He determined the destruction of David. He laid his plans with much artifice; he executed them with zeal and diligence; and when he had, as he supposed, the grave of David digged, he fell into it himself! The metaphor is taken from pits dug in the earth, and slightly covered over with reeds &c. so as not to be discerned from the solid ground; but the animal steps on them, the surface breaks, and he falls into the pit and is taken. "All the world agrees to acknowledge the equity of that sentence, which inflicts upon the guilty the punishment intended by them for the innocent." - Horne.