Musannaf Ibn Abi Shayba 16:797

Abu Bakr narrated to us, he said: Abu Usamah narrated to us, from Abd al-Malik, who said: Ata was asked about dyeing with wusmah (woad). He said: "It is among what the people have innovated. I have seen a group of the companions of the Messenger of Allah, may Allah bless him and grant him peace, and I did not see any of them dyeing with wusmah. They would not dye except with henna and katam, and this yellow color."