كتاب الحج
15  
The Book of Pilgrimage
(17)
Chapter: Clarifying the types of Ihram; and that it is permissible to perfom Hajj that is Ifrad, Tamattu and Qiran. It is permissible to join Hajj to Umrah. And when the pilgrim who is performing Qiran should exit Ihram
(17)
باب بَيَانِ وُجُوهِ الإِحْرَامِ وَأَنَّهُ يَجُوزُ إِفْرَادُ الْحَجِّ وَالتَّمَتُّعِ وَالْقِرَانِ وَجَوَازِ إِدْخَالِ الْحَجِّ عَلَى الْعُمْرَةِ وَمَتَى يَحِلُّ الْقَارِنُ مِنْ نُسُكِهِ
Sahih Muslim 1211 r

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.
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا ابْنُ عُلَيَّةَ، عَنِ ابْنِ عَوْنٍ، عَنْ إِبْرَاهِيمَ، عَنِ الأَسْوَدِ، عَنْ أَمِّ الْمُؤْمِنِينَ، ح وَعَنِ الْقَاسِمِ، عَنْ أُمِّ الْمُؤْمِنِينَ، قَالَتْ قُلْتُ يَا رَسُولَ اللَّهِ يَصْدُرُ النَّاسُ بِنُسُكَيْنِ وَأَصْدُرُ بِنُسُكٍ وَاحِدٍ قَالَ ‏ "‏ انْتَظِرِي فَإِذَا طَهَرْتِ فَاخْرُجِي إِلَى التَّنْعِيمِ فَأَهِلِّي مِنْهُ ثُمَّ الْقَيْنَا عِنْدَ كَذَا وَكَذَا - قَالَ أَظُنُّهُ قَالَ غَدًا - وَلَكِنَّهَا عَلَى قَدْرِ نَصَبِكِ - أَوْ قَالَ - نَفَقَتِكِ ‏"‏ ‏.‏
Reference : Sahih Muslim 1211r
In-book reference : Book 15, Hadith 136
USC-MSA web (English) reference : Book 7, Hadith 2781
  (deprecated numbering scheme)