Al-Kāfi - Volume 3 > One’s having Little Water on a Journey but Is Afraid of Facing Thirst
Hadith #2

2ـ الْحُسَيْنُ بْنُ مُحَمَّدٍ عَنْ مُعَلَّى بْنِ مُحَمَّدٍ عَنِ الْحَسَنِ بْنِ عَلِيٍّ الْوَشَّاءِ عَنْ حَمَّادِ بْنِ عُثْمَانَ عَنِ ابْنِ أَبِي يَعْفُورٍ قَالَ سَأَلْتُ أَبَا عَبْدِ الله (عَلَيْهِ الْسَّلام) عَنِ الرَّجُلِ يُجْنِبُ وَمَعَهُ مِنَ الْمَاءِ قَدْرُ مَا يَكْفِيهِ لِشُرْبِهِ أَ يَتَيَمَّمُ أَوْ يَتَوَضَّأُ قَالَ التَّيَمُّمُ أَفْضَلُ أَ لاَ تَرَى أَنَّهُ إِنَّمَا جُعِلَ عَلَيْهِ نِصْفُ الطَّهُورِ.

2. Al-Husayn ibn Muhammad has narrated from Mu‘alla’ ibn Muhammad from al-Hassan ibn Ali al-Washsha’ from Hammad ibn ‘Uthman from ibn abu Ya‘fur who has said the following: “I once asked abu ‘Abd Allah, ‘Alayhi al-Salam, about a man who experiences sexual relation and has enough water only for his drinking needs; must he take Tayammum or Wudu’? He (the Imam) said, ‘Tayammum is better. You should understand the fact that the task of cleansing is made only half as much in his favor.’”