The Book of Pilgrimage (Kitab Al-Hajj) 
Muslim :: Book 7 : Hadith 2802
Jabir b. 'Abdullah (Allah be pleased with them) reported: We came with the Messenger of Allah (May peace be upon him) pronouncing Talbiya for Hajj, and the Messenger of Allah (May peace be upon him) commanded us to make (our Ihram) into that of Umra.
FAREWELL PILGRIMAGE OF THE APOSTLE OF ALLAH (MAY PEACE BE UPON HIM)
Just as the first revelation in the cave of Hira' marks the advent of the apostolic mission of Muhammad (May peace be upon him), similarly his Farewell Pilgrimage marks its crowning glory. Opinions differ as to when Hajj became obligatory but the commonly accepted opinion is that it was in the eighth year of Hijra that Allah declared it as one of the five fundamentals of Islam. In the ninth year of Hijra the Holy Prophet (may peace be upon him) sent Abu Bakr as the leader of the Hajj delegation but he himself did not go. Hadrat Abu Bakr was later on joined by Hadrat Ali in order to make a sure declaration on behalf of the Holy Prophet (may peace be upon him) which concerned the freedom from obligation in regard to those idolatrous tribes who had shown no respect for the treaties which they had entered into with the Holy Prophet (May peace be upon him). This declaration is contains in the opening verses of Sura Tauba.
The Holy Prophet (May peace be upon him) spent this year in making preparations for the Hajj in the tenth year of Hijra which coincided with the sixty-third year (the last year) of his life. Every attempt was, therefore, made to take full advantage of this great assembly. Messengers were sent to all parts of Arabia inviting people to join him in this great Pilgrimage. It was necessary for them since they should learn by first-hand knowledge the several injunctions and practices of the Pilgrimage-free from all taints of ignorance-an ideal pattern which was to be kept intact in its pristine glory for all times to come. Not only the rites and rituals of the Pilgrimage were to be finally explained by the Holy Prophet (May peace be upon him) but all those things which had any concern with Islam had been finalized.
The Holy Prophet (May peace be upon him) delivered a khutba on the 24th of Dhi-Qa'da on the occasion of the Friday prayer and gave the Muslims necessary instructions relating to Hajj. Next day, I. e. on the 25th of Dhi-Qa'da, he set out after Zuhr prayer on a journey for Hajj along with thousands of his devoted Companions. The 'Asr prayer was offered at Dhu'l-Hulaifa. The caravan spent the night there and it was there after the Zuhr prayer that the Holy Prophet (May peace be upon him) and his Companions put on Ihram and proceeded towards Mecca. They reached their destination on the 4th of Dhu'l-Hijja pronouncing Talbiya (Labbaik, Labbaik, Allahumma Labbaik).
As the caravan moved on the number of participants swelled till, according to some of the narrators, it reached more than one lakh and thirty thousands. The Farewell Pilgrimage is one of the most important occasions in the sacred life of Muhammad (May peace be upon him). Apart from the rites and rituals, the addresses and speeches of the Holy Prophet (May peace be upon him) succinctly sum up the teachings of Islam.