Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
There are three views on when hajj was made obligatory on Muslim: It was said that hajj was enjoined in 5 AH or 6 AH or 9 AH. It is, however, more probable that it was instituted either on the ninth or the tenth of Hijrah.
Responding to your question, Sheikh Ahmad Kutty, a senior lecturer and an Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states:
There is a difference of opinion among scholars regarding the exact year the hajj (Pilgrimage) was instituted, although all of them agree that it was after the institution of prayer, zakah, and fasting. There are three views: sixth, ninth or tenth. It is, however, more probable that hajj was instituted either on the ninth or the tenth of Hijrah.
The verse enjoining hajj (Quran 3:97) was revealed in the year of delegations, which was the ninth year. Although hajj was instituted in the ninth year, the Prophet (peace be upon him) delayed it until the Kabha was purged of the idols. He sent Abu Bakr (may Allah be pleased with him) as the leader in the first hajj, and then he performed it next year, which was the only hajj he performed in Islam.
Almighty Allah knows best.