Jamieson, Fausset and Brown on Revelation 16:2

2. went--Greek, "went away."

poured out--So the angel cast fire into the earth previous to the series of trumpets (Re 8:5).

upon--so Coptic. But A, B, C, Vulgate, and Syriac read, "into."

noisome--literally, "evil" (compare De 28:27, 35). The very same Greek word is used in the Septuagint as here, Greek, "helkos." The reason why the sixth Egyptian plague is the first here is because it was directed against the Egyptian magicians, Jannes and Jambres, so that they could not stand before Moses; and so here the plague is sent upon those who in the beast worship had practiced sorcery. As they submitted to the mark of the beast, so they must bear the mark of the avenging God. Contrast Re 7:3; Eze 9:4, 6.

grievous--distressing to the sufferers.

sore upon the men--antitype to the sixth Egyptian plague.

which had the mark of the beast--Therefore this first vial is subsequent to the period of the beast's rule.