ثُمَّ بَعَثْنَـٰهُمْ لِنَعْلَمَ أَىُّ ٱلْحِزْبَيْنِ أَحْصَىٰ لِمَا لَبِثُوٓا۟ أَمَدًا
Summa ba'asnaahum lina'lama ayyul hizbaini ahsaa limaa labisooo amadaa
Then We woke them so that We could make clear which of the two parties was better able to work out how long they had been there.
Then we awakened them, so we would know which of the two groups had better reckoned the length of their stay.