Musannaf Ibn Abi Shayba 16:793

Abu Bakr narrated to us, he said: Ibn Numayr narrated to us, from Isra'il, from 'Abd al-A'la, who said: I asked Ibn al-Hanafiyyah about dyeing with woad (al-wasmah), and he said: "It is our dye, the people of the house (Ahl al-Bayt)."