Types of Hajj (Hadith No. 890)

Volume 2, Book 20, Number 191:
Narrated Ibn Abbas:
The Prophet and his companions reached Mecca in the morning of the 4th Dhul-Hijja reciting Talbiya (O Allah! We are obedient to Your orders, we respond to Your call) intending to perform Hajj. The Prophet ordered his companions to assume the lhram for Umra instead of Hajj, excepting those who had Hadi (sacrifice) with them.
Prophet (SAW) stayed in Makkah for 10 days for Hajj, according to Hadith no. 187.
Why did Prophet (SAW) ordered some people to assume Ihraam for Umrah instead of Hajj? Background information on Hajj needed.

There are three types of Hajj: Tamattu’, Ifraad and Qiraan. 

Tamattu’ means entering ihraam for ‘Umrah only during the months of Hajj (the months of Hajj are Shawwaal, Dhu’l-Qi’dah and Dhu’l-Hijjah; see al-Sharh al-Mumti’, 7/62). When the pilgrim reaches Makkah he performs tawaaf and saa’i for ‘Umrah, and shaves his head or cuts his hair, and exits ihraam. Then when the day of al-Tarwiyah, which is the 8th of Dhu’l-Hijjah, comes, he enters ihraam for Hajj only, and does all the actions of Hajj. So Tamattu’ involves a complete ‘Umrah and a complete Hajj.

Ifraad means entering ihraam for Hajj only. When the pilgrim reaches Makkah he performs tawaaf al-qudoom (tawaaf of arrival) and saa’i for Hajj, but he does not shave or cut his hair and does not exit ihraam, rather he remains in ihraam until he exits ihraam after stoning Jamarat al-‘Aqabah on the day of Eid.  If he delays the saa’i of Hajj until after the tawaaf of Hajj, there is nothing wrong with that. 

Qiraan means entering ihraam for ‘Umrah and Hajj both together. Or entering ihraam for ‘Umrah first then including Hajj in that before starting the tawaaf of Hajj. That is done by intending that his tawaaf and saa’i will be for both Hajj and ‘Umrah.  
The actions done in Qiraan are the same as those done in Ifraad, except that the pilgrim doing Qiraan has to offer a hadiy (sacrifice) whereas the pilgrim doing Ifraad does not. 

The best of these three types of Hajj is Tamattu’. This is what the Prophet (peace and blessings of Allaah be upon him) enjoined upon his companions and urged them to do. Even if a person enters ihraam for Qiraan or Ifraad, then it is strongly recommended for him to change his intention to ‘Umrah, then complete ‘Umrah and exit ihraam, so that he will then be doing Tamattu’. He may do that after doing tawaaf al-qudoom and saa’i  – because when the Prophet (peace and blessings of Allaah be upon him) did tawaaf and saa’i during his Farewell Pilgrimage, and his companions were with him, he told everyone who did not have a sacrificial animal (hadiy) to change his intention and make his ihraam for ‘Umrah and to cut his hair and exit ihraam, and he said, “Were it not that I have brought the hadiy with me, I would do what I have commanded you to do.”

So, the ones who had brought animals along for sacrifice were doing Qiraan, and the rest were ordered to intend for Tamattu`.