Ibn Hajar reported: Ash-Shafi’ee, may Allah have mercy on him, said, “Innovations are of two kinds: praiseworthy and blameworthy. Whatever agrees with the Sunnah is praiseworthy and whatever differs from it is blameworthy.”

In another narration, Ash-Shafi’ee said, “Newly invented matters are of two types. Whatever is invented that differs from the Book, the Sunnah, the reports, and the consensus, then this is called an innovation of misguidance. Whatever goodness is invented that does not differ in any way from those, then this is called an innovation that is not blameworthy.”

Source: Fath ul-Bari 6849

عن ابن حجر قَالَ الشَّافِعِيُّ الْبِدْعَةُ بِدْعَتَانِ مَحْمُودَةٌ وَمَذْمُومَةٌ فَمَا وَافَقَ السُّنَّةَ فَهُوَ مَحْمُودٌ وَمَا خَالَفَهَا فَهُوَ مَذْمُومٌ

عَنِ الشَّافِعِيِّ أَيْضًا قَالَ الْمُحْدَثَاتُ ضَرْبَانِ مَا أُحْدِثُ يُخَالِفُ كِتَابًا أَوْ سُنَّةً أَوْ أَثَرًا أَوْ إِجْمَاعًا فَهَذِهِ بِدْعَةُ الضَّلَالِ وَمَا أُحْدِثُ مِنَ الْخَيْرِ لَا يُخَالِفُ شَيْئًا مِنْ ذَلِكَ فَهَذِهِ مُحْدَثَةٌ غَيْرُ مَذْمُومَةٍ

6849 فتح الباري شرح صحيح البخاري كِتَاب الِاعْتِصَامِ بِالْكِتَابِ وَالسُّنَّةِ المحدثات