1.    When Hajj was prescribed:   

“And Hajj (pilgrimage to Makkah) to the House (Ka’bah) is a duty that mankind owes to Allaah, those who can afford the expenses (for one’s conveyance, provision and residence).” [Aal ‘Imraan 3:97]  

The ruling of Hajj:

Hajj is a fareedah (obligatory duty), one of the pillars of Islam. The evidence (daleel) for this is the aayah mentioned above, and there is also evidence in the Sunnah which indicates the same thing.

Ibn ‘Umar (may Allaah be pleased with them both) said: the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Islam is built upon five (pillars): testifying that there is no god but Allaah and that Muhammad is the Messenger of Allaah, establishing regular prayer, paying zakaah, Hajj and fasting Ramadaan.” (Narrated by al-Bukhaari, 8; Muslim, 16).

3.    Is Hajj obligatory straight away?  

Yes, it should be done straight away. The evidence for this is the aayah referred to above. This (doing things straight away) is the guiding principle concerning the commands of sharee’ah. The evidence in the Sunnah which indicates this is as follows:

a.      Abu Hurayrah said: The Messenger of Allaah (peace and blessings of Allaah be upon him) gave a sermon (khutbah) and said: “O people, Allaah has enjoined Hajj upon you so do Hajj.” (Narrated by Muslim, 1337).

b.     Ibn ‘Abbaas (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever wants to go for Hajj, let him hasten to do it, because he may fall ill or some other problems may arise.” (Narrated by Abu Dawood, 1732, without the phrase “because he may…” also narrated by Ibn Maajah, 2883 and Ahmad, 1836).

According to a report narrated by Ahmad “Hasten to do Hajj –i.e., the obligatory Hajj – for none of you knows what may happen to him.”

These two reports strengthen one another. (See Irwaa’ al-Ghaleel by al-Albaani, 4/168).

The Shaafa’is say that Hajj may be delayed, because the Prophet (peace and blessings of Allaah be upon him) delayed his Hajj until 10 AH. But the answer to this is as follows:

a.      He only delayed it for one year, but they say it may be delayed indefinitely!

b.     He (peace and blessings of Allaah be upon him) wanted to purify the House (the Ka’bah) of the Mushrikeen and those who performed Hajj naked.

c.     He was kept busy with the delegations who had started to come to Madeenah one after another to announce their Islam.

(See al-Sharh al-Mumti’ by Shaykh Ibn ‘Uthaymeen, 7/17, 18)

4. It is obligatory to do Hajj once in one's lifetime

Abu Hurayrah said: The Messenger of Allaah (peace and blessings of Allaah be upon him) gave a sermon (khutbah) and said: “O people, Allaah has enjoined Hajj upon you so do Hajj.” A man said, Is it every year, O Messenger of Allaah? He remained silent until the man had said it three times, then he said, “If I say yes, it will become obligatory and you will not be able to do it.” Then he said, “Do not push me to tell you more than what I have left you with, for those who came before you were destroyed because they asked too many questions and argued with their Prophets. If I command you to do a thing, do as much of it as you can, and if I forbid you to do something, then avoid it.” (Narrated by Muslim, 1337)