Narrated `Amr bin `Amir: Anas said, "The Prophet used to perform ablution for every prayer." I asked Anas, "What did you used to do?' Anas replied, "We used to pray with the same ablution until we break it with Hadath."
Hadith Referenceصحيح البخاري / كتاب الوضوء / 214
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة
Narrated Suwaid bin Nu`man: In the year of the conquest of Khaibar I went with Allah's Apostle till we reached As-Sahba' where Allah's Apostle led the `Asr prayer and asked for the food. Nothing but saweeq was brought and we ate it and drank (water). The Prophet got up for the (Maghrib) Prayer, rinsed his mouth with water and then led the prayer without repeating the ablution.
Hadith Referenceصحيح البخاري / كتاب الوضوء / 215
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة