en_tn_lite_do_not_use/luk/17/31.md

let him who is on the housetop not go down

"whoever is on the housetop must not go down" or "if anyone is on his housetop, he must not go down." This is a statement of what people should not do, not a command to the hearers.

on the housetop

Their housetops were flat and people could walk or sit on them.

his goods

"his possessions" or "his things"

return

They are not to go back to the house to get anything. They are to flee quickly. (See: rc://en/ta/man/translate/figs-explicit)