Musnad Ahmad 25:209

Ya'la ibn 'Ubayd narrated to us, Sufyan narrated to us, from 'Abdullah ibn 'Uthman, from Sa'id ibn Jubayr, from Ibn 'Abbas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The best of your kohl is antimony (ithmid); it clears the vision and makes the hair grow."