Hajj is one of the five pillars of Islam. Hajj is obligatory on those who can afford it. Al-Quran and Hadith related to this are presented below:
‘When I made the Kaaba a place of gathering and safety for mankind and said, Make the place where Abraham stood a place of prayer, and commanded Abraham and Ishmael, keep my house sacred for those who pray, stand and bow and prostrate.’ (Surah Baqarah, verse-125)

‘Whoever has the strength and ability to reach Baitullah should perform Hajj and whoever disobeys this command will commit kufr, he should know that Allah does not expect those who dwell on the nature of the world.’ (Surah Al-Imran, verse-97)

‘Surely Safa and Marwa are among the signs of Allah. So the person who completes the Hajj or Umrah of the house of Allah, runs between these two mountains, no sin is possible for him. And whoever does a good deed of his own volition, interest and enthusiasm, Allah is Aware of him and will reward him, He is All-Knowing.’ (Surah Baqarah, verse-158)

‘And proclaim the Hajj among the people, they will come to you from all distant places on foot and on camels. So that they may slaughter the four-footed animals as a sustenance given by Him, remembering the name of Allah for their welfare and on certain days. Then eat from it and feed the needy.’ (Surah Hajj, Verses 27-28)

‘He who is able to go there, it is obligatory upon him to perform Hajj for the sake of Allah. And whoever denies (let him know that), Allah is not dependent on the world.’ (Surah Al-Imran, verse 97)

Hadith related to Hajj:
‘Narrated by Ibn Abbas (RA), Allah's Messenger, may God bless him and grant him peace, said: Make Hajj Umrah and Umrah followers of Hajj.’ (That is, perform Hajj, perform Umrah, and perform Hajj, if performed Umrah.) Because both Hajj and Umrah remove poverty and sin as the (blacksmith's) whetstone removes the impurities of iron.’ (Nasa'i 2630-2631, from Tirmidhi, Nasa'i and other Companions, Tabarani 11033)

‘Abu Hurairah RA. Said, I heard the Prophet, peace and blessings be upon him, saying, ‘Whoever performs Hajj for the sake of Allah and refrains from obscenity and sin, he will return from Hajj as pure as the day he was born from his mother's womb.’ -Sahih Bukhari, Hadith: 1521; Sahih Muslim, Hadith: 1350; Musnad Ahmad, Hadith: 7381; Sunan Ibn Majah, Hadith: 2881; Sunan Nasa'i 5/114; Sahih Ibn Hibban, Hadith: 3694; Sahih Ibn Khuzaima, Hadith: 2514