The Recognition of the End of the Night
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 36
سَأَلَ عُمَرُ بْنُ حَنْظَلَةَ أَبَا عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ فَقَالَ لَهُ: زَوَالُ اَلشَّمْسِ نَعْرِفُهُ بِالنَّهَارِ كَيْفَ لَنَا بِاللَّيْلِ فَقَالَ «لِلَّيْلِ زَوَالٌ كَزَوَالِ اَلشَّمْسِ» قَالَ فَبِأَيِّ شَيْءٍ نَعْرِفُهُ قَالَ «بِالنُّجُومِ إِذَا اِنْحَدَرَتْ.
Umar ibn Hanthala asked Imam Jafar ibn Muhammad Al-Sadiq عليه السلام saying: "We recognize the zenith (midday) of the sun during the day; how can we recognize the zenith during the night?" Imam عليه السلام said: "The night has a zenith just like the zenith of the sun." Umar then asked: "And by what means do we recognize it?" Imam عليه السلام said: "By the stars when they descend”.
- Ṣaḥīḥ al-Faqīh