Before him went the pestilence, and burning coals went forth at his feet.
Before him went the pestilence - to destroy His people's foes, as He smote the Philistines with emerods, so that they said, "Send away the ark of the God of Israel ... that it slay us not. For there was a deadly destruction throughout all the city; the hand of God was very heavy there" (1 Samuel 5:9; 1 Samuel 5:11). As Yahweh's advent is glorious to His people, so it is terrible to His foes.
Burning coals - Psalms 18:8 ("There went up a smoke out of His nostrils, and fire out of His mouth devoured; coals were kindled by it") favours the English version. Others, on account of the parallelism (as margin), translate, 'burning disease' (cf. Deuteronomy 32:24, "They shall be devoured with burning heat" Hebrew, burning coals х reshep (H7565)], the same Hebrew as here; Psalms 91:6). But it seems to me more poetical to tranalate as the English version, retaining the metaphor "burning coals" put metaphorically for burning pestilence. So the requirement of the parallelism is quite sufficiently met.
Went ... at his feet - i:e., after Him, as His attendants (Judges 4:10).