"They used to sleep but little of the night." Al-Hasan's interpretation: He says, they would not sleep of it except for a little.
﴿كَانُوا قَلِيلا مِنَ اللَّيْلِ مَا يهجعون﴾ تَفْسِير الْحسن: يَقُول: كَانُوا لَا ينامون مِنْهُ إِلَّا قَلِيلا.