وَيَقُولُونَ مَتَىٰ هَـٰذَا ٱلْوَعْدُ إِن كُنتُمْ صَـٰدِقِينَ
Wayaqooloona mat a h atha alwaAAdu in kuntum sa diqeen a And [when] they ask, "When is this promise [of resurrection] to be fulfilled? [Answer this, O you who believe in it,] if you are men of truth!" -
 - Mohammad Asad
They also say: "When will this promise be fulfilled if what you say be true?"
 - Muhammad Farooq-i-Azam Malik
They ask 'the believers', 'When will this threat come to pass, if what you say is true?'
 - Mustafa Khattab
And they say: When (will) this promise (be fulfilled), if ye are truthful?
 - Marmaduke Pickthall
They also say: "When will this promise (come to pass)? (Say) if ye are truthful."
 - Abdullah Yusuf Ali