كتاب الصيام
13  
The Book of Fasting
(12)
Chapter: Clarifying that Kissing when fasting is not unlawful for the one whose desire is not provoked by that
(12)
باب بَيَانِ أَنَّ الْقُبْلَةَ فِي الصَّوْمِ لَيْسَتْ مُحَرَّمَةً عَلَى مَنْ لَمْ تُحَرِّكْ شَهْوَتَهُ ‏‏
Sahih Muslim 1106 h

It is further narrated on the authority of Aswad and Masruq that they went to the Mother of the Believers and they asked her (and the rest of the hadith is the same)

وَحَدَّثَنِيهِ يَعْقُوبُ الدَّوْرَقِيُّ، حَدَّثَنَا إِسْمَاعِيلُ، عَنِ ابْنِ عَوْنٍ، عَنْ إِبْرَاهِيمَ، عَنِ الأَسْوَدِ، وَمَسْرُوقٍ أَنَّهُمَا دَخَلاَ عَلَى أُمِّ الْمُؤْمِنِينَ يَسْأَلاَنِهَا ‏.‏ فَذَكَرَ نَحْوَهُ ‏.‏
Reference : Sahih Muslim 1106h
In-book reference : Book 13, Hadith 86
USC-MSA web (English) reference : Book 6, Hadith 2442
  (deprecated numbering scheme)