But they [only] ask, "When is this promise to be fulfilled? [Answer this, O you who believe in it,] if you are men of truth!"

They ask: When will this promise be (fulfilled)? - If ye are telling the truth.

And they say: When (will) this promise (be fulfilled), if ye are truthful?

And they say: When will this threat be (executed), if you are truthful?

And they say, "When is this promise, if you should be truthful?"