﴿ وَيَقُولُونَ مَتَىٰ هَٰذَا ٱلْوَعْدُ إِن كُنتُمْ صَٰدِقِينَ ﴾

“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!” –”

Please check ayah 27:75 for complete tafsir.