Sayyiduna Anas (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) forbade "making nabidh in gourd vessels and pitch-coated vessels", and Sayyiduna Abu Hurayrah (may Allah be pleased with him) would also forbid hollowed tree-root vessels and green jars.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17470