Charles H. Spurgeon on Psalms 29:7

Divideth the flames of fire. Margin, cutteth out. The Hebrew word (bux) khatzab means properly to cut, to hew, to hew out; as for example, stones. The allusion here is undoubtedly to lightning; and the image is either that it seems to be cut out, or cut into tongues and streaks —or, more probably, that the clouds seem to be cut or hewed, so as to make openings or paths for the lightning. The eye is evidently fixed on the clouds, and on the sudden flash of lightning, as if the clouds has been cleaved or opened for the passage of it. The idea of the psalmist is, that the "voice of the Lord, "or the thunder, seems to cleave or open the clouds for the flames of fire to play amidst the tempest. Albert Barnes.