Sayyiduna Itban (may Allah be pleased with him), or, as the narrator doubts, perhaps Sayyiduna Ibn Itban al-Ansari (may Allah be pleased with him), narrates: I said: "O Messenger of Allah, I was with my wife, and when I heard your voice I withdrew and took a ritual bath." The Prophet (peace and blessings be upon him) said: "Water (the bath) is only required because of water (ejaculation)."
Ahmad recorded it, and its chain is hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الطهارة / 1431