When he uttereth his voice, etc. The phrase is difficult, but the Authorized Version probably gives the right sense. God's "voice" is the thunder (Psalms 29:3), which is accompanied by the gathering of heavy clouds ("His pavilion round about him," Psalms 18:11).
He causeth the vapors to ascend, etc.; the storm-clouds coming up more and more thickly from the horizon. From this point the verse agrees with Psalms 135:7 (the psalm is full of such reminiscences, and is obviously very late).
Lightning's with rain; rather, for the rain. The lightning's are, as it were, the heralds or attendants of the rain. The wind out of his treasures; a noble figure, used elsewhere of the snow and hail (Job 38:22), and of the waters of the sea (Psalms 33:7).