Riyad as-Salihin

Sa'b bin Jaththamah (May Allah be pleased with him) reported: I presented a wild ass to Messenger of Allah (ﷺ) as a gift but he returned it to me. When he perceived signs of despair on my face, he said, "I have declined to accept it because I am in the state of Ihram."

[Al-Bukhari and Muslim].