Sahih Muslim Book 7, Hadith Number 2851.

Chapter : One who undertakes to perform Umra is not allowed to put off Ihram before Sai’ and the pilgrim and the (Qiran) is not allowed to put off ihram at Tawaf Qud’um (circumambulation of arrival).

Asma bint Abu Bakr (Allah be pleased with both of them) reported: We set out (to Mecca) in a state of Ihram. Allah’s Messenger (may peace be upon him) said: He who has the sacrificial animal with him should remain in the state of Ihram, but he who has not the sacrificial animal with him should put off Ihram. As I had not the sacrificial animal with me, I put off Ihram. And since Zubair (her husband) had the sacrificial animal with him, he did not put off Ihram. She (Asma) said: I put on my clothes and then went out and sat by Zabair, whereupon he said: Go away from me, whereupon I said: Do you fear that I would jump upon you?