Sayyiduna Anas (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) led the Zuhr prayer in Madinah with four rak'ahs while we were with him, and he (peace and blessings be upon him) led the Asr prayer at Dhul-Hulayfah with two rak'ahs. Then he spent the night there, and in the morning he mounted his riding camel. When it climbed onto al-Bayda', he (peace and blessings be upon him) said 'Allahu akbar' (Allah is the Greatest), 'Subhan Allah' (Glory be to Allah) and 'Al-hamdu lillah' (All praise is for Allah), then he entered ihram with the talbiyah for Hajj and Umrah, and then the people also entered ihram with the talbiyah for Hajj and Umrah. When we arrived (in Makkah), he (peace and blessings be upon him) commanded them: "Change it into Umrah," and then they entered ihram for Hajj on the 8th of Dhul-Hijjah. The Messenger of Allah (peace and blessings be upon him) slaughtered seven camels with his own hand while they were standing, and in Madinah he (peace and blessings be upon him) sacrificed two horned black-and-white rams.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10213