Muwatta Malik, Book 18, Hadith 19 (USC-MSA)

Yahya related to me from Malik from Zayd ibn Aslam from Ata ibn Yasar that Abdullah ibn Abbas was asked about people kissing while fasting and he said that he allowed it for old men but disapproved of it for young men.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ زَيْدِ بْنِ أَسْلَمَ، عَنْ عَطَاءِ بْنِ يَسَارٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عَبَّاسٍ، سُئِلَ عَنِ الْقُبْلَةِ، لِلصَّائِمِ فَأَرْخَصَ فِيهَا لِلشَّيْخِ وَكَرِهَهَا لِلشَّابِّ ‏.‏

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also referenced under: Book 18, Hadith 653 (In-Book)