Hajj is one of the five pillars of Islam. It is a set of bodily, financial and ritual acts of worship.
It is that unique trip in the world of travel whereby a Muslim moves with his body and heart to the City of Security (Mecca) by which Allah has sworn in the Quran, where he stands in Arafat and circumumbulates the Sacred House, which Islam has ordained as a symbol of Allah's unification and the unity of Muslims, and ordained for every Muslim to turn towards it five times in his/her prayers.

﴾And wheresoever you people are, turn your faces (in prayer) in that direction.﴿

[Al-Baqarah, 144]

 Then Allah ordained that Muslims have to go to the Sacred House, and circumambulate it once in a lifetime.
 The Ancient House (Ka'bah) is the first house built for people. It is the first place built on earth for worshipping Allah. Prophet Ibrahim and his son Isma'il rebuilt it. Those two noble prophets are the fathers of this Muslim nation and Allah has accepted their sincere supplication when they were building the Sacred House. Allah says:

﴾And (remember) when Ibrahim (Abraham) and (his son) Isma'il (Ishmael) were raising the foundations of the House (the Ka'bah at Makkah), (saying), "Our Lord! Accept (this service) from us. Verily! You are the All-Hearer, the All-Knower."*"Our Lord! And make us submissive unto You and of our offspring a nation submissive unto You, and show us our Manasik (all the ceremonies of pilgrimage - Hajj and 'Umrah, etc.), and accept our repentance. Truly, You are the One Who accepts repentance, the Most Merciful.*"Our Lord! Send amongst them a Messenger of their own (and indeed Allah answered their invocation by sending Muhammad Peace be upon him ), who shall reauthor unto them Your Verses and instruct them in the Book (this Qur'an) and Al-Hikmah (full knowledge of the Islamic laws and jurisprudence or wisdom or Prophethood, etc.), and sanctify them. Verily! You are the All-Mighty, the All-Wise."﴿

[Al-Baqarah 127-129]

 The prophet (PBUH) said:

(( I am the supplication of Ibrahim and the glad tidings of Issa, the son of Maryam))

  Hajj is a practical proof that a believer gives to his Lord and to himself, that accepting Allah's invitation- out of love for Allah and seeking His content- is better for him than his wealth, family, children, job, and country.
 Thus, this act of worship is distinguished as it needs full dedication because it can be only performed in Allah's Sacred House…
 A pilgrim has to leave his country, his family and his friends, bear the rigors of travel, and face its dangers, pay money seeking Allah's content. However, if the price of this act of worship is high, its fruit is great as well.
  The prophet (PBUH) said:

((Whoever performs Hajj (pilgrimage) and does not have sexual relations (with his wife), nor commits sin, nor disputes unjustly (during Hajj), then he returns from Hajj as pure and free from sins as on the day on which his mother gave birth to him.))

 He also said:

((Al-Hajj effaces pre-Hajj sins))
((The reward of a properly performed Hajj is no less than Paradise.))
((The pilgrims performing Hajj and ‘Umrah are a delegation to Allah. If they call upon Him, He will answer them; and if they ask for His forgiveness, He will forgive them.))

 Thus, the prophet (PBUH) said:

((Keep at it between Hajj and Omrah, for they negate poverty and sins just as Al-kir removes the scum of iron, gold and silver))
((Spending in Hajj is akin to spending in the cause of Allah.))

  Al-Hajj is a mandatory, individualistic obligation to be performed by each male and female Muslim, who should be an adult, sane, free, and who can afford it, once in a lifetime. Those who deny it are considered unbelievers and those who abandon it are considered iniquitous.
 The prophet (PBUH) said:

((Whoever has the provisions and the means to convey him to Allah's House and he does not perform Hajj, then it does not matter if he dies as a Jew or a Christian.))

 Hajj is the fifth pillar of Islam. This is well-known in religion. The prophet (PBUH) said:

((“Islam is built around five (pillars):the testimony that there is no god except Allah and that Muhammad (PBUH) is His slave and Messenger, to establish prayer, to give Zakaat (obligatory charity), to fast in Ramadhan, and to perform Hajj (pilgrimage) for those who can afford it.))

 Al-Hajj (pilgrimage to Mecca) is a set of verbal, genial, bodily, financial and ritualistic acts of worship that are performed at specially designated places, times and in a specific manner. If prayers are performed five times a day, Friday prayer is performed once a week, and fasting is performed once a year, Hajj is an obligation once in a lifetime, as the prophet (PBUH) said:

((It is due only once. If performed more than once, it would be by way of voluntary acts of worship.))

 Al-Hajj is a trip to Allah. His will has so decreed, for an absolute wise purpose, in view of the natural disposition in every human being – to establish on earth for people a House of His that enables those who believe in Him to head to it, from every far away point (on earth) in order to express their love to Allah and their yearning to Him. Thus, a believer affirms through his heading to the Sacred House, in obedience to his Lord's call, that he loves Allah more than his family, children, money, country and all people..Thus he bears the expenditures of Hajj that may be exorbitant and bears leaving family and children, which may be difficult to bear. He bears abandoning his business and the profit that may be quite abundant – all this out of his love of Allah and in hope of winning proximity to Him.
  Allah's wisdom ordained that His Inviolable House be situated in the hot region of the earth, in a valley that has no vegetation, in order to make it clear to pilgrims that sincere communication with Allah is a source of bliss for men that enables them to dispense with all material comfortable circumstances that create an illusion of being the cause of their happiness, and that man's happiness emanates from his inner self, not from the kind of pleasure with which they surround themselves.

 Had Allah's Inviolable House been situated in the temperate region of the earth that abounds with green mountains, crystal-clear water, beautiful lakes, lush gardens, pleasant atmosphere and fresh breeze, and had Hajj been ordained all the year round for precluding congestion, then all people would have rushed to perform a pleasant duty in pursuit of enjoyment, not prompted by the love of the Creator of the Universe.
 Allah the Al-Mighty says:

﴾"O our Lord! I have made some of my offspring to dwell in an uncultivable valley by Your Sacred House (the Ka'bah at Makkah); in order, O our Lord, that they may perform As-Salat (Iqamat-as-Salat), so fill some hearts among men with love towards them, and (O Allah) provide them with fruits so that they may give thanks.﴿

[Ibrahim, 37]

  In addition to the location of the Inviolable House and its climate, a pilgrim is prohibited from wearing sewn clothes and from using all types of perfume, from having his hair cut and shortened, and is prohibited from indulging in the pleasures that are permitted outside the Hajj rites. All this is for enhancing his communication with Allah and enjoying His proximity alone, being remote from all earthly distractions, so that the pilgrim would become certain that if he attains to divine proximity, he would have won everything and that all the pleasures of the world could not secure sustained happiness. Hence, he would sincerely say, "O, Lord, what would a person miss if he finds You? And what would a person find if he misses You?