Bulugh al-Maram, Book 1, Hadith 153 (English)

In another version by Al-Bukhari, he said: "And perform ablution for every Salat (prayer)". Abu Dawud and others transmitted a similar narration.

وَفِي رِوَايَةٍ لِلْبُخَارِيِّ: { وَتَوَضَّئِي لِكُلِّ صَلَاةٍ } وَهِيَ لِأَبِي دَاوُدَ وَغَيْرِهِ مِنْ وَجْهٍ آخَرَ.‏

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also referenced under: Book 1, Hadith 171 (In-Book)