Musnad Ahmad 32:1804

Husayn narrated to us, Jarir narrated to us, from Muhammad, from Anas, who said: The head of al-Husayn was brought to Ubayd Allah ibn Ziyad, and it was placed in a basin. He began to poke it, and he said something regarding his beauty. Anas said: "He was the most resembling of them to the Messenger of Allah, may Allah bless him and grant him peace, and he was dyed with woad."