Umrah is a cleanser for the sins committed between it and another Umrah. - al-Bukhari Muslim
To perform one Umrah in Ramadan is equal to a Hajj in reward. In another narration, it is equal to a Hajj performed with the Prophet [PBUH]. Muslim.
The performers of Hajj and Umrah represent (the order of) Allah Ta'ala. If they call Him, He answers them; and if they seek His Forgiveness, He forgives them. Ibn Majah
Abdullah ibn Masud [R.A] reports that Rasulullah [PBUH] said, "Perform Hajj and Umrah one after the other. Surely they remove poverty and sins just as the furnace removes the rust from iron, gold and silver." at-Tirmidhi an-Nasa'i
A'ishah [R.A] once sought permission from Rasulullah [PBUH] to go for Jihad. Rasulullah [PBUH] replied, "Your Jihad is Hajj." Ahmad
If a person sets off for Hajj or Umrah and passes away on route, he shall be brought before Allah Ta'ala without having to stand for judgement, nor will he have to give account. It shall be said to him: 'Enter into Jannah.' at-Targhib