Therefore hell hath enlarged herself, and opened her mouth without measure: and their glory, and their multitude, and their pomp, and he that rejoiceth, shall descend into it. Therefore hell - the grave; Hebrew, Shª'owl (H7585); Greek, Hadees (G86), the unseen world of spirits. Not here the place of torment.
Hath enlarged herself. Poetically, it is represented as enlarging itself immensely, in order to receive the countless hosts of Jews which should perish (Numbers 16:30).
Their glory, and their multitude - i:e., of the Jewish people.
And he that rejoiceth - the drunken reveller in Jerusalem.
Shall descend into it.