As smoke is driven away - To wit, by the wind. Smoke - vapor - easily disturbed and moved by the slightest breath of air - represents an object of no stability, or having no power of resistance, and would thus represent the real weakness of the most mighty armies of men as opposed to God.
So drive them away - With the same ease with which smoke is driven by the slightest breeze, so do the enemies of God disappear before his power. Compare the notes at Psalms 1:4.
As wax melteth before the fire - Compare Psalms 22:14. The meaning here is plain. As wax is melted down by fire - losing all its hardness, its firmness, its power of resistance, so must the most mighty armies melt away before God.
So let the wicked perish at the presence of God - That is, those who rise up against him; his enemies. It will be as easy for God to destroy wicked men as it is for fire to melt down wax.