The Book of Hajj
24/5. Chapter:
The Virute Of 'Umrah
Sunan an-Nasai
أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، عَنْ مَالِكٍ، عَنْ سُمَىٍّ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " الْعُمْرَةُ إِلَى الْعُمْرَةِ كَفَّارَةٌ لِمَا بَيْنَهُمَا وَالْحَجُّ الْمَبْرُورُ لَيْسَ لَهُ جَزَاءٌ إِلاَّ الْجَنَّةُ " .
It was narrated that abnu Hurairah said: "The Messenger of Allah said: 'from one 'Umrah to another is an expiation for what comes in between, and Hajj al-Mabrur brings no reward less than Paradise.'''(sahih)
Reference : Sunan an-Nasa'i 2629In-book reference : Book 24, Hadith 11English translation : Vol. 3, Book 24, Hadith 2630