"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]])
# any human bone
Bones would be all that remained of the corpses after a period of time.
# they will put a marker by it, until gravediggers come and bury it
There are apparently two groups of men. The first will mark the location of corpses, and the second group will bury them.