[Machine] I heard the Messenger of Allah ﷺ saying, "Women must observe forty days of postnatal bleeding." "This is a confirmed Sunnah (practice) because this chain of narration, starting from Abu Bilal, is sound and authentic. However, Al-Hasan did not hear it directly from Uthman ibn Abi al-'As, but he has a similar chain of narration as testimony." This statement is attributed uniquely to Abu Bilal al-Ash'ari via Ibn Shihab. If it is sound in transmission from him, then it is an authentic hadith. However, Al-Hasan did not hear directly from Uthman ibn Abi al-'As, but he has a similar chain of narration as testimony.  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ «وُقِّتَ لِلنِّسَاءِ فِي نِفَاسِهِنَّ أَرْبَعِينَ يَوْمًا» «هَذِهِ سُنَّةٌ عَزِيزَةٌ فَإِنَّ سَلِم هَذَا الْإِسْنَادُ مِنْ أَبِي بِلَالٍ فَإِنَّهُ مُرْسَلٌ صَحِيحٌ فَإِنَّ الْحَسَنَ لَمْ يَسْمَعْ مِنْ عُثْمَانَ بْنِ أَبِي الْعَاصِ وَلَهُ شَاهِدٌ بِإِسْنَادٍ مِثْلِهِ» تفرد به أبو بلال الأشعري عن ابن شهاب فإن سلم منه فإنه مرسل صحيح فإن الحسن لم يسمع من عثمان بن أبي العاص وله شاهد