Abu Dawud Book 4, Hadith Number 1984.
Narated By Umm Ma’qil : When the Apostle of Allah (PBUH) performed the Farewell Pilgrimage, and we had a camel, AbuMa’qil dedicated it to the cause of Allah. Then we suffered from a disease, and AbuMa’qil died. The Prophet (PBUH) went out (for hajj). When he finished the hajj, I came to him.
He said (to me): Umm Ma’qil, what prevented you from coming out for hajj along with us?
She said: We resolved (to do so), but AbuMa’qil died. We had a camel on which we could perform hajj, but AbuMa’qil had bequeathed it to the cause of Allah.
He said: Why did you not go out (for hajj) upon it, for hajj is in the cause of Allah? If you miss this hajj along with us, perform umrah during Ramadan, for it is like hajj.
She used to say: hajj is hajj, and umrah is umrah. The Apostle of Allah (PBUH) said it to me: I do not know whether it was peculiar to me.