Fiqh-us-Sunnah Volume 5, Hajj and ‘Umrah, Fiqh 5.002A.

Abu Hurairah reported that the Prophet (peace be upon him) said: “He who performs Hajj for Allah’s pleasure and avoids all lewdness and sins will return after Hajj free from all sins as he was the day his mother gave birth to him.” (Bukhari and Muslim)

‘Amr ibn al-‘As says: “When Allah guided me to Islam, I went to the Prophet (peace be upon him) and said to him: ‘O Prophet of Allah! Stretch out your hand so that I may pledge my allegiance to you.’ The Prophet (peace be upon him) stretched out his hand to me, but I withdrew my hand. The Prophet (peace be upon him) asked: ‘O ‘Amr! what is the matter with you?’ I said: ‘I would like to stipulate a condition!’ The Prophet (peace be upon him) asked: ‘What is it?’ I said: ‘That all my past sins be forgiven!’ The Prophet (peace be upon him) said: ‘O ‘Amr! Do you not know that Islam wipes off all past sins, and hijrah (leaving one’s home and hearth for Allah’s cause) wipes off all sins, and (similarly) Hajj wipes off all past sins!”‘ (Muslim)

Abdullah ibn Mas’ud narrated that the Prophet (peace be upon him) said: “Alternate between Hajj and ‘Umrah (regularly), for these two remove poverty and sins just as the blacksmith’s bellows removes all impurities from metals like iron, gold and silver. The reward for Hajj Mabrur is nothing short of Paradise.” (Nasa’i and Tirmizhi, who regards it a sound hadith)