Sahih Bukhari Volume 3, Book 47, Hadith Number 768.
Narated By ‘Abdullah bin ‘Abbas : That he heard As-Sa’b bin Jaththama Al-Laithi, who was one of the companions of the Prophet, saying that he gave the meat of an onager to Allah’s Apostle while he was at a place called Al-Abwa’ or Waddan, and was in a state of Ihram. The Prophet did not accept it. When the Prophet saw the signs of sorrow on As-Sa’b’s face because of not accepting his present, he said (to him), “We are not returning your present, but we are in the state of Ihram.” (See Hadith No. 747)