Musannaf Ibn Abi Shayba 23:215

'Abd al-Rahman ibn Mahdi narrated to us, from Sufyan, from his father, who said: I heard Ibrahim al-Taymi saying: "Nothing compelled me to this sitting of mine except that I saw as if I were smelling sweet basil among the people." So I mentioned that to Ibrahim al-Nakha'i, and he said: "Indeed, sweet basil has a [pleasant] appearance, but its taste is bitter."