Sahih Muslim Book 23, Hadith Number 4934.

Chapter : It is forbidden to prepare Nabidh is varnished jar, gourd, green pitcher, and hollow stumps.

Ibn ‘Umar reported: Allah’s Messenger (may peace be upon him) addressed people in one of his expeditions. Ibn ‘Umar said: I went forward to him but he went away before I reached him. I asked (the people present there): What did he say? They said that he (the Holy Prophet) had forbidden the preparation of Nabidh in gourd and varnished jar.