Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
darimi:991Jaʿfar b. ʿAwn > Ismāʿīl b. Muslim > al-Ḥasan > ʿUthmān b. Abū al-ʿĀṣ > And Qt al-Nufasāʾ Arbaʿīn Yawm

[Machine] "The period of postnatal bleeding is forty days, so if she becomes pure before that, then she can resume prayers, but if not, she should not perform them until she does."  

الدارمي:٩٩١أَخْبَرَنَا جَعْفَرُ بْنُ عَوْنٍ أَنبَأَنَا إِسْمَاعِيلُ بْنُ مُسْلِمٍ عَنِ الْحَسَنِ عَنْ عُثْمَانَ بْنِ أَبِي الْعَاصِ قَالَ

«وَقْتُ النُّفَسَاءِ أَرْبَعِينَ يَوْمًا فَإِنْ طَهُرَتْ وَإِلَّا فَلَا تُجَاوِزْهُ حَتَّى تُصَلِّيَ»