Muwatta Malik, Book 18, Hadith 17 (USC-MSA)

Yahya related to me from Malik from Zayd ibn Aslam that Abu Hurayra and Sad ibn Abi Waqqas used to say that someone who was fasting was allowed to kiss.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ زَيْدِ بْنِ أَسْلَمَ، أَنَّ أَبَا هُرَيْرَةَ، وَسَعْدَ بْنَ أَبِي وَقَّاصٍ، كَانَا يُرَخِّصَانِ فِي الْقُبْلَةِ لِلصَّائِمِ ‏.‏

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also referenced under: Book 18, Hadith 650 (In-Book)