Moses is referring to an event in the past when Dathan and Abiram rebelled against Moses and Aaron. The full meaning of this statement can be made explicit. (See: [[rc://en/ta/man/translate/figs-explicit]])
# Dathan ... Abiram ... Eliab
These are names of men. (See: [[rc://en/ta/man/translate/translate-names]])
# son of Reuben
"descendant of Reuben"
# earth opened its mouth and swallowed them up
Yahweh causing the land to split open so that the people fell in is spoken of as if the land had a mouth and the ability to swallow people. (See: [[rc://en/ta/man/translate/figs-personification]])