Hajj is one of most important pillars of Islam and it is one of greatest religious duties.
Holy Qur’an says in a short and meaningful sentence:
وَ لِلّه عَلَى النّاسِ حِجُّ الْبَیْتِ مَنِ اسْتَطاعَ اِلَیْهِ سَبیلاً
It is on people for the sake of Allah to perform Hajj of his house, anyone who is able to undertake the journey to him. (2:196)
And it says below this verse:
وَ مَنْ کَفَرَ فَاِنَّ اللّهَ غَنِىٌّ عَنِ الْعالَمینَ
And anyone who disbelieves (and renounces Hajj, has impaired himself), Allah is not in need of any of his created ones in the worlds.”(3:97)
The sentence “It is on people for the sake of Allah …” adding the definition of “disbelieves” (infidelity) for people who renounce the obligatory Hajj. This clears shows it’s extraordinary importance in Islam.
It is interesting that in the interpretation of the holy verse:
وَ مَنْ کانَ فى هذِهِ اَعْمى فَهُوَفِى الاْخِرَةِ اَعْمى وَ اَضَلُّ سَبیلاً
And anyone who had been blind (from seeing Allah) in this world, will be blind in hereafter and more deviant from the path”. (17:72)