From Sahih Muslim (Hadith 2927):
AI-Qasim narrated from the Mother of the Believers (Hadrat 'A'isha) that she said:Messenger of Allah. the people return (from Mecca) having done two worships (both Hajj and Umra), but I am coming back with one (only). whereupon he said: You should wait and when the period of menses is over, you should go to Tan'im and put on lhram and then meet us at such and such time (and I think he said tomorrow) ; and (the reward of this Umra) is for you equal to your hardship or your spending
Reference: Muslim 2927