‘Before him went the pestilence,
And fiery bolts (burning coals, thunderbolts, fearsome heat, plague) went forth at his feet,
He stood and measured the land (or ‘earth'),
He beheld and drove asunder the nations,
And the eternal mountains were scattered,
The everlasting hills did bow,
His goings were of old.
The ‘fiery bolts' (burning coals), translated as burning heat, and therefore plague in Deuteronomy 32:24, or thunderbolts in Psalms 78:48, represent something burning and fiery.
Because the parallel line has pestilence we are possibly to see it as the burning heat experienced by those who suffer from certain kinds of plague. Faithless Israel was threatened with pestilence in the wilderness (Numbers 13:12), after which God would produce a new nation. And those who did not observe the covenant were promised terrible plagues (Deuteronomy 28:59). But here the thought, while including this, probably refers to God's wider judgments. He is the God Who punishes by pestilence and plague. Compare the words of Jesus in Luke 21:11.
On the other hand pestilence denotes a variety of afflictions, and so it may well be paralleled with thunderbolts. Thus the thought may be of the afflictions that would come on the Canaanites, and on all the enemies of God's true people, as they had on Egypt, softening them up in preparation for the arrival and triumph of His people..
‘He stood and measured the land (or ‘earth'), He beheld and drove asunder the nations.' Again we have reference to the entry into Canaan as God conducts affairs and leads His people, especially through the captain of His host (Joshua 5:14). First He is seen as weighing up the land. And then He drove asunder the nations before His people But He will also do this on a universal scale. He also measures the whole earth and there too has His way on the nations.
‘And the eternal mountains were scattered, the everlasting hills did bow, His goings were of old (or ‘were everlasting').' Even that which is most permanent could not, and cannot, resist His coming. The eternal mountains and the everlasting hills give way before Him and yield to His presence (see Nahum 1:5). For He is the eternal God, and His ways are of old, even from everlasting, from before time began.