كتاب الحج
10  
The Book of Hajj
(233)
Chapter: The Obligation of Hajj (Pilgrimage) and its Excellence
(233)
- باب وجوب الحج وفضله
Riyad as-Salihin 1278
Ibn 'Abbas (May Allah be pleased with them) reported:
The Prophet (ﷺ) said, "(The performance of) 'Umrah during Ramadan is equal to Hajj (pilgrimage)." Or said, "Equal to the performance of Hajj with me."

[Al-Bukhari and Muslim].

وعن ابن عباس رضي الله عنهما، أن النبي صلى الله عليه وسلم قال‏:‏ ‏ "‏عمرة في رمضان تعدل عمرة أو حجة معي‏"‏‏.‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏
Reference : Riyad as-Salihin 1278
In-book reference : Book 10, Hadith 8