Amr bin Aamir asked Hazrat Anas (may Allah be pleased with him) about performing ablution for every prayer, so he replied that the Prophet (peace and blessings be upon him) used to perform a fresh ablution for every prayer, and we used to offer several prayers with a single ablution until we became without ablution.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 12565
Hadith Gradingحکم دارالسلام:حديث صحيح، خ: 214، وهذا إسناد ضعيف لضعف شريك لكنه متابع