John Gill Commentary Psalms 7:15

"He hath made a pit, and digged it, And is fallen into the ditch which he made." — Psalms 7:15 (ASV)

He made a pit and dug it That is, he dug a pit, and made it very large and capacious, to answer his purposes;

and is fallen into the ditch [which] he made; so it is said of the Heathen, (Psalms 9:15); and is exemplified in the case of Haman, who was hanged upon the gallows he had built for Mordecai. Kimchi explains this of Saul's falling upon his own sword, and dying by it, which he drew against David; phrase is proverbial, (Proverbs 26:27) (Ecclesiastes 10:8); the sense of this and the above figurative expressions is literally and properly given in (Psalms 7:16).