Al-Kāfi - Volume 3 > Things Coming Out of a Dead Body after Ghusl (bath)
Hadith #3

3ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ بَعْضِ أَصْحَابِهِ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ الْسَّلام) قَالَ إِذَا خَرَجَ مِنَ الْمَيِّتِ شَيْ‏ءٌ بَعْدَ مَا يُكَفَّنُ فَأَصَابَ الْكَفَنَ قُرِضَ مِنْهُ.

3. Ali ibn Ibrahim has narrated from his father from ibn abu ‘Umayr from certain persons of his people who has said the following: “Abu ‘Abd Allah, ‘Alayhi al-Salam, has said, ‘If after shrouding a certain part of it (cloth) becomes unclean, it must be cut off and disposed.’”