Yahya related to me from Malik from Humayd ibn Qays from Ata ibnRabah that a bedouin came to the Messenger of Allah, may Allah blesshim and grant him peace, when he was at Hunayn, and he was wearing ashirt with traces of yellow on it. He said, "Messenger of Allah, Ihave entered ihram for umra. What should I do?" The Messenger ofAllah, may Allah bless him and grant him peace, said to him, "Take offyour shirt and wash off this yellowness and do in umra as you would doon hajj."
USC-MSA web (English) reference: Book 20, Hadith 18
Arabic reference: Book 20, Hadith 727