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 s

Ibn al-Muththanna reported on the authority of Ibn Abu'Adi who transmitted on the authority of Ibn'Aun who narrated from al-Qasim and Ibrahim having said:

I cannot differentiate the hadith of one from the other (Qasim and Ibrahim) that the Mother of the Believers (Allah be pleased with her) said this: Messenger of Allah, people have come back with two acts of worship. The rest of the hadith is the same.
وَحَدَّثَنَا ابْنُ الْمُثَنَّى، حَدَّثَنَا ابْنُ أَبِي عَدِيٍّ، عَنِ ابْنِ عَوْنٍ، عَنِ الْقَاسِمِ، وَإِبْرَاهِيمَ، - قَالَ لاَ أَعْرِفُ حَدِيثَ أَحَدِهِمَا مِنَ الآخَرِ - أَنَّ أُمَّ الْمُؤْمِنِينَ - رضى الله عنها - قَالَتْ يَا رَسُولَ اللَّهِ يَصْدُرُ النَّاسُ بِنُسُكَيْنِ ‏.‏ فَذَكَرَ الْحَدِيثَ ‏.‏
Reference : Sahih Muslim 1211s
In-book reference : Book 15, Hadith 137
USC-MSA web (English) reference : Book 7, Hadith 2782
  (deprecated numbering scheme)