Al-Kāfi - Volume 3 > The Quantity of Water Required for Wudu’, Showers and One Who Is Excessive in the Use of Water for Wudu’
Hadith #2

2ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ وَمُحَمَّدُ بْنُ إِسْمَاعِيلَ عَنِ الْفَضْلِ بْنِ شَاذَانَ عَنْ حَمَّادٍ عَنْ حَرِيزٍ عَنْ زُرَارَةَ وَمُحَمَّدِ بْنِ مُسْلِمٍ عَنْ أَبِي جَعْفَرٍ (عَلَيْهِ الْسَّلام) قَالَ إِنَّمَا الْوُضُوءُ حَدٌّ مِنْ حُدُودِ الله لِيَعْلَمَ الله مَنْ يُطِيعُهُ وَمَنْ يَعْصِيهِ وَإِنَّ الْمُؤْمِنَ لاَ يُنَجِّسُهُ شَيْ‏ءٌ إِنَّمَا يَكْفِيهِ مِثْلُ الدَّهْنِ.

2. Ali ibn Ibrahim has narrated from his father and Muhammad ibn ’Isma‘il from al-Fadl ibn Shadhan from Hammad from Hariz from Zurarah and Muhammad ibn Muslim who has said the following: “Abu Ja‘far, ‘Alayhi al-Salam, has said, ‘Wudu’ is one of the boundaries Allah has established so that He finds out who obeys or disobeys Him. The believing people do not allow it (their body) to remain unclean. It is sufficient to use a small amount of water like rubbing oil on one’s body.’”