كتاب الحج
15  
The Book of Pilgrimage
(36)
Chapter: The virtue of the Umrah performed during Ramadan
(36)
باب فَضْلِ الْعُمْرَةِ فِي رَمَضَانَ ‏
Sahih Muslim 1256

Ibn Abbis reported that Allah's Apostle (ﷺ) said to a woman of the Ansar who was called Umm Sinan:

What has prevented you that you did not perform Hajj with us? She said: The father of so and so (i. e. her husband) had only two camels. One of them had been taken away by him (my busbard) and his son for Hajj, whereas the other one is used by our boy to carry water. Upon this he (the Holy Prophet) said: Umra during the month of Rawadin would suffice for Hajj or Hajj along with me.
وَحَدَّثَنَا أَحْمَدُ بْنُ عَبْدَةَ الضَّبِّيُّ، حَدَّثَنَا يَزِيدُ، - يَعْنِي ابْنَ زُرَيْعٍ - حَدَّثَنَا حَبِيبٌ، الْمُعَلِّمُ عَنْ عَطَاءٍ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ لاِمْرَأَةٍ مِنَ الأَنْصَارِ يُقَالُ لَهَا أُمُّ سِنَانٍ ‏"‏ مَا مَنَعَكِ أَنْ تَكُونِي حَجَجْتِ مَعَنَا ‏"‏ ‏.‏ قَالَتْ نَاضِحَانِ كَانَا لأَبِي فُلاَنٍ - زَوْجِهَا - حَجَّ هُوَ وَابْنُهُ عَلَى أَحَدِهِمَا وَكَانَ الآخَرُ يَسْقِي عَلَيْهِ غُلاَمُنَا ‏.‏ قَالَ ‏"‏ فَعُمْرَةٌ فِي رَمَضَانَ تَقْضِي حَجَّةً ‏.‏ أَوْ حَجَّةً مَعِي ‏"‏ ‏.‏
Reference : Sahih Muslim 1256
In-book reference : Book 15, Hadith 245
USC-MSA web (English) reference : Book 7, Hadith 2885
  (deprecated numbering scheme)