Al-Kāfi - Volume 3 > Blood Because of Childbirth
Hadith #6

6ـ مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ ابْنِ فَضَّالٍ عَنِ ابْنِ بُكَيْرٍ عَنْ زُرَارَةَ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ الْسَّلام) قَالَ تَقْعُدُ النُّفَسَاءُ أَيَّامَهَا الَّتِي كَانَتْ تَقْعُدُ فِي الْحَيْضِ وَتَسْتَظْهِرُ بِيَوْمَيْنِ.

6. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from ibn Faddal from ibn Bukayr from Zurarah who has said the following: “Abu ‘Abd Allah, ‘Alayhi al-Salam, has said, ‘A woman for giving birth waits for the number of days of her Hayd (menses); then she must examine in two days.’”