Surah Saba Tafseer

And they say:"When is this promise if you are truthful!"

This is like the Ayah:

يَسْتَعْجِلُ بِهَا الَّذِينَ لَا يُوْمِنُونَ بِهَا وَالَّذِينَ ءَامَنُواْ مُشْفِقُونَ مِنْهَا وَيَعْلَمُونَ أَنَّهَا الْحَقُّ

Those who believe not therein seek to hasten it, while those who believe are fearful of it, and know that it is the very truth... (42:18)

Then Allah says:

قُل لَّكُم مِّيعَادُ يَوْمٍ لاَّ تَسْتَأْخِرُونَ عَنْهُ سَاعَةً وَلَا تَسْتَقْدِمُونَ