The legal opinion they used to give, that water is required only after the emission of water, was a concession granted by the Messenger of Allah in the early days of Islam. He later commanded that the full bath be performed in any case.
حدثنا محمد بن مهران البزاز الرازي حدثنا مبشر الحلبي عن محمد أبي غسان عن أبي حازم عن سهل بن سعد
أن الفتيا التي كانوا يفتون أن الماء من الماء كانت رخصة رخصها رسول الله في بدء الإسلام ثم أمر بالاغتسال بعد
[Its chain of transmission is sahih]. Darimi narrated it in the Book of Purification, Chapter on Water Is Only Needed Due to Water (i.e., seminal discharge), no. 766, from Muhammad bin Mihran Jammal, through this same route, and Ibn Majah also narrated it, no. 609.