«عَمَلُوكْ مِسَحَّرْ؟ قَالْ: فِرِغْ رَمَضَانْ»

Set up as a brief question and reply, the saying answers news of someone's new post as Ramadan's pre-dawn waker with a flat letdown: that job exists only during Ramadan, and the month has already ended. The humor lies in timing, since the role arrives exactly when nothing is left for it to do.

It fits anyone who takes up a task only to see its purpose run out while they are at it, so their effort is no longer wanted. It may tease someone's bad luck or simply note that a service became unnecessary just as somebody stepped in; context decides which, so not every use is a complaint about fate.

Use it wryly when someone takes on a job or task only to find it pointless by the time they start: work that evaporates on arrival, help offered after the need has passed. It suits teasing or rueful self-mockery.