Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada , states: “Hajj in order to be valid or proper must fulfil the following pillars as well as essentials:
First let me list the pillars (arkan) without which one misses the Hajj altogether; then we will list the essentials.
The pillars of Hajj are: Intention and ihram; standing in the plains of Arafat, performing tawaf al-ifadah and the ritual of sa’y (running) between the hill locks of Safa and Marwah and finally shaving or trimming of the hair.
Although no one doubts the importance of any of the above, the above list is according to the Shafi`ie school; the Hanafis, however, do not consider ihram as a rukn but as a condition for the validity of Hajj, which is the same thing. Hanafis consider shaving or trimming hair not as a pillar but as an essential.
Now coming to the essentials or wajibat, they are the following:
1. Ihram at the prescribed station or prior to reaching there; it must be done during the months of Hajj;
2. pelting the stone pillars’
3. Sacrifice for those who perform tamattu or qiran forms of Hajj; if they cannot afford they can expeate through fasting;
4. Shunning all the sinful activities and all actions and behaviour that may invalidate the Hajj;
5. Tawaf of arrival is essential according to Malikis, although no one denies its importance;
6. Performing Salah of tawaf is essential according to Hanafis but others consider it a Sunnah;
7. Sa`y between the two hill locks is an essential, according to Hanafis, which can be compensated for by sacrifice if a person misses it, but others consider it as rukn.
8. Shaving or trimming of hair is rukn according to shafis; but it is wajib according to the other three imams.
9. Farewell tawaf is essential according to Imams: Abu Hanifah, Shafi`ie and Ahmad, but is Sunnah, according to Imam Malik, may Allah be pleased with them all.
10. Spending at least some time during the night in Muzdalifah while returning from Arafat before proceeding to mina
It should be made clear that none of the above-mentioned Imams consider any of the above as less important; they are only differing about the precise technicality of describing each of the above-mentioned rites.
Finally, while the form of Hajj is important, the spirit and soul of Hajj are also important. They are related to focusing on the inner aspects of Hajj. At the heart of Hajj is remembrance of Allah and readiness to respond to His call, and fulfilling it with a spirit of utter love and devotion. For this I recommend that you read the Four Pillars of Islam by Mawlana Sayyid Abu Hasan Ali Nadvi. May Allah make your Hajj a Hajj mabrur (virtuous Hajj)-ameen.”

Allah Almighty knows best.