"so that the designated men may bury the dead bodies"
# to cleanse the land ... purify the land
In Jewish law, a dead body defiled anything it touched and made it "unclean." Burying these bodies is spoken of as cleansing or purifying the land. (See: [[rc://en/ta/man/translate/figs-explicit]] and [[rc://en/ta/man/translate/figs-metaphor]])
# seventh month
This "seventh" is the ordinal number for seven. (See: [[rc://en/ta/man/translate/translate-ordinal]])