Sayyiduna Imam al-Hasan bin Ali (may Allah be pleased with him) narrates: When the Prophet (peace and blessings be upon him) performed ablution, he would save some water, so that he could pour it over the place of his prostration.
Al-Tabarani recorded it in al-Mu'jam al-Kabir, and its chain is hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1190