Bulugh al-Maram, Book 3, Hadith 8 (In-Book)

A’ishah (RAA) reported That Abu Bakr kissed the Prophet after he had died.’ Related by Al-Bukhari.

وَعَنْهَا { أَنَّ أَبَا بَكْرٍ اَلصِّدِّيقَ ‏- رضى الله عنه ‏- قَبَّلَ اَلنَّبِيَّ ‏- صلى الله عليه وسلم ‏-بَعْدَ مَوْتِهِ } رَوَاهُ اَلْبُخَارِيُّ 1‏.‏ ‏1 ‏- صحيح.‏ رواه البخاري (8/146‏-147 و 10/166/فتح)‏.‏

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also referenced under: Book 3, Hadith 564 (English)