So, give them tidings of a painful torment.
Promise them painful retribution
Therefore give to them glad tidings of a painful punishment
So announce to them a painful chastisement
So announce good news to them with (of) a painful torture
O’ Mohammad, let people know that there is a terrible punishment awaiting them
Therefore give them the glad tidings of a painful punishment
So give them tidings of a painful punishment
So give them the news of a painful punishment
So (do not bother about them, rather) give them the news of a woeful punishment
So announce to them a painful torment