Related for Berakhot 44:33

A man who had a seminal emission (Baal Keri) and is sick, if nine Kavs of water were poured on him, he may read [the Shema]. But he may not fulfill the obligation [of reading the Shema] for others until he dips himself in forty Seah [of water]. Rebbi Yehudah says, “Forty Seah no matter what."