Language:
كتاب العمرة
26  
`Umrah (Minor pilgrimage)
(4)
Chapter: 'Umra in (the month of) Ramadan
(4)
باب عُمْرَةٍ فِي رَمَضَانَ
Sahih al-Bukhari 1782

Narrated Ata:

I heard Ibn `Abbas saying, "Allah's Messenger (ﷺ) asked an Ansari woman (Ibn `Abbas named her but `Ata' forgot her name), 'What prevented you from performing Hajj with us?' She replied, 'We have a camel and the father of so-and-so and his son (i.e. her husband and her son) rode it and left one camel for us to use for irrigation.' He said (to her), 'Perform `Umra when Ramadan comes, for `Umra in Ramadan is equal to Hajj (in reward),' or said something similar."

حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، عَنِ ابْنِ جُرَيْجٍ، عَنْ عَطَاءٍ، قَالَ سَمِعْتُ ابْنَ عَبَّاسٍ ـ رضى الله عنهما ـ يُخْبِرُنَا يَقُولُ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم لاِمْرَأَةٍ مِنَ الأَنْصَارِ سَمَّاهَا ابْنُ عَبَّاسٍ، فَنَسِيتُ اسْمَهَا ‏"‏ مَا مَنَعَكِ أَنْ تَحُجِّي مَعَنَا ‏"‏‏.‏ قَالَتْ كَانَ لَنَا نَاضِحٌ فَرَكِبَهُ أَبُو فُلاَنٍ وَابْنُهُ ـ لِزَوْجِهَا وَابْنِهَا ـ وَتَرَكَ نَاضِحًا نَنْضَحُ عَلَيْهِ قَالَ ‏"‏ فَإِذَا كَانَ رَمَضَانُ اعْتَمِرِي فِيهِ فَإِنَّ عُمْرَةً فِي رَمَضَانَ حَجَّةٌ ‏"‏‏.‏ أَوْ نَحْوًا مِمَّا قَالَ‏.‏
Reference : Sahih al-Bukhari 1782
In-book reference : Book 26, Hadith 9
USC-MSA web (English) reference : Vol. 3, Book 27, Hadith 10
  (deprecated numbering scheme)