Hajj, also known as the greater pilgrimage, is an amazing phenomenon which engulfs the hearts and minds of Muslims from all across the globe. It is an event which is indeed spectacular; a mass sea of human will and flesh surging along the path once traversed by Abraham , the caller to Islamic monotheism. It is a pilgrimage that is centered around the prime maxim of monotheism, every action and ritual maintaining a direct relationship with it.
Inasmuch as Hajj being the single most important and spiritual journey that man will undertake, it is pertinent to note that most are unaware of the Qur'anic verses relating to it. It is in this vein that we shall be taking a brief look at a few verses in Surah Hajj where Allah speaks of this most blessed journey.
The discussion begins with the verse,
|"And (remember) when We appointed for Abraham the place of the House (saying) 'Do not ascribe anything as a partner to Me and purify My House for those who circumbulate, stand, bow, and prostrate.'"|
The verse commences the discussion about Hajj through introducing it as an affair which stems from Abraham. We find that the appointment of the house (Kabah) coupled with pure monotheism as Allah established for Abraham His House along with His house rules. In keeping with His guidelines, He articulates acceptable and pleasing behavior: circumbulating, standing, bowing, and prostration - all forms of physical worship. Thus, the verse in question affirms tawhid (monotheism), the action of tawhid (al-Uluhiyah), the direction (qiblah) of tawhid, and the Prophet of tawhid. It is through such points that man may achieve eternal bliss; by believing in the monotheistic nature of Allah without ascribing any form of partnership to him, by worshipping Him in line with His monotheistic nature through the prescribed actions of circumbulating, standing, bowing, and prostrating; facing the Kabah while committing these acts; and following the millah (religion) of Abraham who was a monotheist himself.
Abraham , the Friend of Allah , is given sole importance in relation to the Kabah, and was honored through being commanded to build the Kabah where Allah decreed. It was built out of taqwa and founded upon obedience, he and his son built this great edifice and a part of his offspring remained in Makkah living alongside it. As for Allah's command to purify His House, it was to purify it from polytheism and disobedience, and from impurities and dirt. Allah, the Most High, ascribes the House to himself through His usage of the pronoun 'my', and in doing so sanctified and honored this blessed structure. It is to this end that `Umar b. Al-Khattab said when kissing the black stone, "Verily I know that you are merely a stone, you neither harm nor benefit. Were it not for the fact that the Prophet kissed you, I never would have,"  since his kiss was merely because of its sanctified nature which God afforded it, and not because it is special in and of itself.
Allah then says,
|"And proclaim unto mankind the Pilgrimage. They will come to you on foot and on every lean camel; they will come from every deep ravine, so that they may witness things that are of benefit to them, and mention the name of Allah on appointed days over the beast of cattle that He has bestowed upon them. Then eat thereof and feed therewith the poor unfortunate."|
After being commanding to build the sanctified structure, Abraham was told to call mankind to undertake the pilgrimage. It is mentioned the Abraham said, "My Lord, how can I call mankind when my voice cannot reach them?" So it was said, "Call, and its conveyance is upon us." Similarly, the famous exegete Ibn Al-'Arabi states that "Allah commanded him to climb Abi Qubais  and call out, "O mankind, Allah has ordained upon you the Hajj, so undertake the Pilgrimage." So none were left except that Allah conveyed the call of Abraham to them..." 
The verse then states the means by which the pilgrims shall respond to the call, and their coming from "every deep ravine" is from every far and desolate place, so much so that the believers will flock from all corners of the earth - this miraculous statement is evident today where people of all nationalities and races arrive at the sacred House. Interestingly Allah states that "they will come to you" as in to Abraham instead of the House itself. This passage emphasizes the link between the Hajj and Abraham, and that the Hajj is to respond to the call of monotheism - it is in effect an act of monotheism. Furthermore, in responding to Abraham we become of him, as Allah states "Verily, among mankind who have the best claim to Abraham are those who followed him."  Thus, the Hajj establishes the connection between the Muslims and Abraham since we are the only people to follow in his way, in both deed and intent.
As for "the things that are of benefit", they are of two types: religious and worldly. As for the religious benefit, it is to engage in worship and fulfill one's duty to Allah . As for the worldly gain, it is to gain an income and some profit. Ibn `Abbas said the verse pertained to benefit in this life and the hereafter. "As for benefit in the hereafter, it is to reside in eternal bliss; and as for this life, it is benefit in regards to profit and business undertakings."  In this regards, the majority of exegetes state that the meaning of the verse "There is no sin on you if you seek the Bounty of your Lord..."  is that there is no harm nor sin in undertaking profitable ventures during the Hajj as long as it does not interfere with carrying out the prescribed rituals.
In regards to mentioning the name of Allah on the appointed days, then this is to slaughter the sacrifice in His Glorious name as well as to praise and thank Allah for His many bounties. Ibn `Abbas stated the 'appointed days' are the first ten days of the month of Dhul Hijjah.  The 'beast of cattle' is recorded in the Qur'an as the bahimatul an'am which are camels, cows, and sheep. This is reiterated by the hadith of `Abdullah b. `Abbas as narrated by Abu Jamrah Nasr b. `Imran Ad-Duba'ī when he asked Ibn `Abbas about the tamattu' Hajj and sacrifice.  In reference to the discussion pertaining to the benefits of Hajj, the bahimatul an'am are also a benefit in this life and the next since the one selling them benefits financially, and the one who slaughters them benefits in the hereafter. It is then from the divine mercy and wisdom of Allah the Most High that he allows the slaughterer (who now benefits from his sacrifice in this life) and the poor to eat from the sacrificial meat.
In ending the Hajj, Allah says,
|"Then let them make an end of their unkemptness and pay their vows and go around the ancient House."|
Their 'unkemptness' is the hair on their heads that they have let grow and been unable to fully comb or cut during their time in the state of ihram, and 'to make and end' is to either shave or trim one's hair. As for paying their vows, it is the promises they have made to the Almighty concerning their Hajj, `Umrah or sacrifice. They are then ordered to complete their Hajj by means of the tawaf al-ifadah, the principle circumambulation of the ancient House. The House is stated as being ancient since Allah says that "first House (of worship) appointed for mankind was that at Bakkah (Makkah), full of blessing, and guidance for the universe." 
Allah then states,
|"That; and whose extols the sacred things of Allah, it will be well for him in the sight of his Lord."|
The first word of the verse ("that") is to establish the verses which have preceded as being the decisive commands of Hajj and thus means, 'that is the command'. As for extolling the sacred things of Allah , it is extremely important since it is amongst the actions which Allah loves and allows the slave to draw close to his Lord. The 'sacred things' are everything that Allah has made sacred and ordered to be exalted, such as salah (ritual worship), the manasik (rituals of Hajj), the haram (sacred vicinity), the ihram (the state of a pilgrim), the sacrifice, and all other matters that require exaltation and love since all these forms of worship stem from an obedient heart and subservient limbs. It is to this effect that Allah says, "That (is the command). And whoso extols the offerings consecrated to Allah, it surely is from the piety of the hearts." 
The Hajj, just like the other pillars of Islam combines spirituality with physical action and reminds us that monotheism is not only a belief we maintain within our hearts and utter with our lips, but a principle we live out through our actions, regardless as to whether we be pilgrims or in a normal state going about our daily lives.
Source: Islam21C.com - Ahmed Ali
 Its authenticity is agreed upon by the two Imams, Al-Bukhari and Muslim.
 It is also said that he stood on Mount Safa
 Ibn Al-'Arabi, Ahkam Al-Qur'an (exegesis of 22:27)
 Tafsir Ibn Kathir (exegesis of 22:28)
 Al-Bukhari reported it in mu'allaq form
 Its authenticity is agreed upon by the two Imams, Al-Bukhari and Muslim