Musnad Ahmad 1153:780

Aswad ibn Amir narrated to us, he said: Sharik narrated to us, from Khasif, he said: A man narrated to me, sixty years ago, from Aisha, she said: I perfumed my head with incense intensely. The Prophet, peace and blessings of Allah be upon him, said: "O Aisha, do you not know that upon every hair there is a state of ritual impurity (janabah)?"