The Chapter on Obligatory Prayers
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 30
وَقَالَ اَلنَّبِيُّ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ: « «مَنْ كٰانَ يُؤْمِنُ بِاللّٰهِ وَ اَلْيَوْمِ اَلْآخِرِ» فَلاَ يَبِيتَنَّ إِلاَّ بِوَتْرٍ.
The Prophet, said: "Whoever believes in Allah سبحانه وتعالى and the Last Day should not sleep except in a state of Witr (having performed the Witr prayer)”.
- Ṣaḥīḥ al-Faqīh