Abu Dawud Book 4, Hadith Number 1983.
Narated By Umm Ma’qil : AbuBakr ibn AbdurRahman said: The messenger of Marwan whom he sent to Umm Ma’qil reported to me.
She said: AbuMa’qil accompanied the Apostle of Allah (PBUH) during hajj. When he came (to her) she said: You know that hajj is incumbent on me. They walked until they visited him (i.e. the Prophet) and she asked (him): Apostle of Allah, hajj is due from me, and AbuMa’qil has a camel.
AbuMa’qil said: She spoke the truth, I have dedicated it to the cause of Allah.
The Apostle of Allah (PBUH) said: Give it to her, that is in the cause of Allah. So he gave the camel to her.
She then said: Apostle of Allah, I am a woman who has become aged and ill. Is there any action which would be sufficient for me as my hajj?
He replied: umrah performed during Ramadan is sufficient as hajj.