"So set out with your family in a part of the night," meaning: in a portion of the night; and night-travel (sura) only occurs at night.
Muhammad said: It is said of it: Asra and sara.
"And follow in their rear," meaning: be behind them, "and let not any one of you look back," meaning: do not look behind you towards the city.
﴿فَأَسْرِ بِأَهْلِكَ بقطعٍ مِنَ اللَّيْلِ﴾ أَيْ: فِي طائفةٍ مِنَ اللَّيْلِ؛ وَالسُّرَى لَا يَكُونُ إِلا لَيْلا.
قَالَ محمدٌ: وَيُقَالُ مِنْهُ: أَسْرَى وسرى.
﴿وَاتبع أدبارهم﴾ أَيْ: كُنْ آخِرَهُمْ ﴿وَلا يَلْتَفِتْ مِنْكُم أحدٌ﴾ لَا يَنْظُرُ وَرَاءَهُ إِلَى الْمَدِينَةِ.
