وَسَنَزِيدُ إِنْ شَاءَ اللَّهُ تَعَالَى شَرْحًا وَإِيضَاحًا فِي مَوَاضِعَ مِنَ الْكِتَابِ عِنْدَ ذِكْرِ الْأَخْبَارِ الْمُعَلَّلَةِ، إِذَا أَتَيْنَا عَلَيْهَا فِي الْأَمَاكِنِ الَّتِي يَلِيقُ بِهَا الشَّرْحُ وَالْإِيضَاحُ إِنْ شَاءَ اللَّهُ تَعَالَى
Translation: We shall, God Most High willing, add further explanation and clarification at places in the book where we discuss reports affected by defects, when we reach the passages suited to that explanation and clarification, God Most High willing.
Muʿallal reports are those affected by a consequential defect established through critical investigation. Not every difference is a defect, nor does the presence of an extra chain automatically remove one. Muslim postpones more detailed illustrations to their proper context rather than asserting a universal verdict here.