صحیح ابن حبان
Ibn Hibban
كتاب الطهارة
Book of Purification
باب الغسل - ذكر البيان بأن ترك الاغتسال من الإكسال كان ذلك في أول الإسلام ثم أمر بالاغتسال منه بعد
Chapter on Ghusl – Clarification that omitting ghusl after ejaculation was in early Islam, then ghusl was later commanded
1 hadith
Hadith 1179
Sayyiduna Sahl bin Sa’d (may Allah be pleased with him) narrates: Sayyiduna Ubayy bin Ka’b (may Allah be pleased with him) informed me of this matter: The issue that people mention, that bathing (ghusl) becomes obligatory only as a result of water (i.e., the emission of semen), was a concession that the Noble Prophet (peace and blessings be upon him) granted in the early days (the narrator is unsure, perhaps these are the words) at the beginning of Islam. Then, after that, he commanded bathing (ghusl). (Imam Ibn Hibban, may Allah have mercy on him, says:) It is possible that Sayyiduna Ubayy bin Ka’b (may Allah be pleased with him) first mentioned the abrogation of this act, as Sayyiduna Sahl bin Sa’d narrated from him. Then he forgot this and gave the fatwa regarding the first ruling about this act, which had been abrogated, as Zayd bin Khalid al-Juhani narrated from him.