Language:
كتاب الجنائز
23  
Funerals (Al-Janaa'iz)
(22)
Chapter: To shroud one in a shirt, stitched or unstitched
(22)
باب الْكَفَنِ فِي الْقَمِيصِ الَّذِي يُكَفُّ أَوْ لاَ يُكَفُّ ، وَمَنْ كُفِّنَ بِغَيْرِ قَمِيصٍ
Sahih al-Bukhari 1270

Narrated Jabir:

The Prophet (ﷺ) came to (the grave of) `Abdullah bin Ubai after his body was buried. The body was brought out and then the Prophet (ﷺ) put his saliva over the body and clothed it in his shirt.

حَدَّثَنَا مَالِكُ بْنُ إِسْمَاعِيلَ، حَدَّثَنَا ابْنُ عُيَيْنَةَ، عَنْ عَمْرٍو، سَمِعَ جَابِرًا ـ رضى الله عنه ـ قَالَ أَتَى النَّبِيُّ صلى الله عليه وسلم عَبْدَ اللَّهِ بْنَ أُبَىٍّ بَعْدَ مَا دُفِنَ فَأَخْرَجَهُ، فَنَفَثَ فِيهِ مِنْ رِيقِهِ وَأَلْبَسَهُ قَمِيصَهُ‏.‏
Reference : Sahih al-Bukhari 1270
In-book reference : Book 23, Hadith 31
USC-MSA web (English) reference : Vol. 2, Book 23, Hadith 360
  (deprecated numbering scheme)