It is narrated from Hazrat Aisha (may Allah be pleased with her) that sometimes ghusl (ritual bath) would become obligatory upon the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) would touch the water with his hand and then go to sleep.
Hadith Referenceمسند احمد / مسند النساء / 25135
Hadith Gradingحکم دارالسلام:حديث صحيح دون قوله: "ولا يمس ماء" ، خ: 1146، م: 739