Sayyidah Maymunah (may Allah be pleased with her) narrates that the Prophet (peace and blessings be upon him) said: "Ablution should not be performed with the water left over from her ritual bath for janabah."
Ahmad recorded it, and its narrators are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1486