The Book of Purification and its Sunnah
1/72. Chapter:
Performing ablution for each prayer and offering all prayers in one ablution
Sunan Ibn Majah
حَدَّثَنَا سُوَيْدُ بْنُ سَعِيدٍ، حَدَّثَنَا شَرِيكٌ، عَنْ عَمْرِو بْنِ عَامِرٍ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ كَانَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ يَتَوَضَّأُ لِكُلِّ صَلاَةٍ وَكُنَّا نَحْنُ نُصَلِّي الصَّلَوَاتِ كُلَّهَا بِوُضُوءٍ وَاحِدٍ .
It was narrated that Anas bin Malik said: "The Messenger of Allah used to perform ablution for every prayer, and we used to perform all of the prayers with one ablution."
Reference : Sunan Ibn Majah 509In-book reference : Book 1, Hadith 243English translation : Vol. 1, Book 1, Hadith 509