Musnad Ahmad 32:507

Rawh narrated to us, Ash'ath narrated to us, from al-Hasan, from Anas ibn Malik, that the Messenger of Allah (may Allah bless him and grant him peace) and his companions arrived in Makkah, and they had entered into the state of Ihram for Hajj and Umrah. The Messenger of Allah (may Allah bless him and grant him peace) commanded them, after they had performed Tawaf around the House and Sa'i between al-Safa and al-Marwah, to exit the state of Ihram and to make it an Umrah. The people were hesitant about that. The Messenger of Allah (may Allah bless him and grant him peace) said: "Were it not that I have brought the sacrificial animal, I would have exited the state of Ihram." So the people exited the state of Ihram and performed Tamattu'.