Albert Barnes Commentary Job 18:8

"For he is cast into a net by his own feet, And he walketh upon the toils." — Job 18:8 (ASV)

For he is cast into a net by his own feet - He is caught in his own tricks, as if he had spread a net or dug a pitfall for another, and had fallen into it himself. The meaning is, that he would bring ruin upon himself while he was plotting the ruin of others; see (Psalms 9:16), The wicked is snared by the work of his own hands; compare the note at (Job 5:13). The phrase “by his own feet” here means, that he walks there himself. He is not led or driven by others, but he goes himself into the net. Wild animals are sometimes driven, but he walks along of his own accord into the net, and has no one to blame but himself.

And he walks upon a snare - Or a pitfall. This was formerly the mode of taking wild beasts. It was done by excavating a place in the earth, and covering it over with turf, leaves, etc. supported in a slender manner; so that the lion, or elephant or tiger that should tread on it, would fall through. These methods of taking wild beasts have been practiced from the earliest times, and are practiced everywhere.