كتاب السلام
39  
The Book of Greetings
(8)
Chapter: The Prohibition Of Being Alone With A Non-Mahram Woman Or Entering Upon Her
(8)
باب تَحْرِيمِ الْخَلْوَةِ بِالأَجْنَبِيَّةِ وَالدُّخُولِ عَلَيْهَا ‏‏
Sahih Muslim 2172 c

Ibn Wahb reported:

I heard Laith b. Said as saying: Al-Hamv means the brother of husband or like it from amongst the relatives of the husband, for example, cousin, etc.
وَحَدَّثَنِي أَبُو الطَّاهِرِ، أَخْبَرَنَا ابْنُ وَهْبٍ، قَالَ سَمِعْتُ اللَّيْثَ بْنَ سَعْدٍ، يَقُولُ الْحَمْوُ أَخُ الزَّوْجِ وَمَا أَشْبَهَهُ مِنْ أَقَارِبِ الزَّوْجِ ابْنُ الْعَمِّ وَنَحْوُهُ ‏.‏
Reference : Sahih Muslim 2172c
In-book reference : Book 39, Hadith 30
USC-MSA web (English) reference : Book 26, Hadith 5402
  (deprecated numbering scheme)