Sahih Muslim Book 7, Hadith Number 2885.

Chapter : Excellence of performing Umra in the month of Ramadhan.

Ibn Abbas reported that Allah’s Apostle (may peace be upon him) 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 husband) 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.