Sayyiduna Ubayy bin Ka'b (may Allah be pleased with him) says: The fatwa "water is from water" was a concession in the early days of Islam; then it was forbidden.
Al-Zuhri did not hear this hadith from Sahl; he heard it only through some of his companions from Sahl.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 775