Sayyiduna Anas (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) would perform ablution with the water left over from his miswak.
Imam al-Bazzar recorded this narration; the narrator al-A'mash did not hear from Sayyiduna Anas (may Allah be pleased with him).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1083