Psalms 18:8 - Joseph Benson’s Commentary on the Old and New Testaments

There went up a smoke out of his nostrils, &c. Here “the further effects of God's indignation are represented by those of fire, which is the most terrible of the created elements, burning and consuming all before it: scorching the ground, and causing the mountains to smoke. Under this appearance God descended on the top of Sinai; thus he visited the cities of the plain; and thus he is to come at the end of time.” Horne. In the poetical figure of the smoke issuing from God's nostrils, the psalmist is thought to allude to the well-known circumstance, that when the passion of anger becomes warm and violent in any man it is wont to discover itself by the heated, vehement breath which proceeds from his nose and mouth. The latter clause of the verse is better rendered, Fire out of his mouth devoured, coals burned from before, or around him.