The Times When Purification is an Obligation
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 5
قَالَ أَبُو جَعْفَرٍ اَلْبَاقِرُ عَلَيْهِ اَلسَّلاَمُ: «إِذَا دَخَلَ اَلْوَقْتُ وَجَبَ اَلطَّهُورُ وَ اَلصَّلاَةُ وَ لاَ صَلاَةَ إِلاَّ بِطَهُورٍ.
Imam Muhammad ibn Ali Al-Baqir عليه السلام said: "When the time for prayer enters, purification (ablution) and the prayer become obligatory, and there is no prayer without purification."
- Ṣaḥīḥ al-Faqīh