John Trapp on Joel 2:6

Verſe 6. Before their face, the people ſhall be much pained,] This is a confirmation of the former aſſertion: the people when they ſhall ſee thoſe ſwarms of Locuſts, &c. muſtering and marching in the air, they ſhall be much pained (as a travelling woman is) pangs and ſorrows ſhall take hold of them, their faces ſhall be as flames, Eſay 13.8. for fear leaſt they ſhould light on their countrey, and lay all waſt.

all faces ſhall gather blackneſſe.] Pallorem, paleneſſe, ſo Caſtalio rendreth it: a blackiſh lead-like-paleneſſe, ſuch as is on ſooty-pots. (the Originall here is, hath gathered a pot, Nigricantem colorem ſignificat. Mercer. that is by a metonymy, a pot-like-blackneſſe) See Nah. 3.10. Jer. 30.6. Pſal. 68.13. where, by blackneſſe (ſuch as ſlaves and ſcullions contract by lying among the pots, and ſmoky, and ſooty chimney-corners) is ſet forth the exceeding great fear, and affliction that Gods people are oft in: and from whence he graciouſly promiſeth to deliver them that truſt in him. Such ſhall not be afraid— whoſe heart is fixed, truſting in the Lord. It was fear that now cauſed (the naturall heat and the blood retiring to the heart, to receive it, as in a ſudden ſurprize, the ſouldiers run to the Caſtle) paleneſſe and blackneſſe of face. It was hunger afterwards, that burnt them, Deut. 32.24. and made their viſages blacker then a cole, (as Lam. 4.8.) or darker then blackneſſe, as the Originall hath it.