Hanafi
The sources give no view for it here.
الحلف على ترك اللبن
هل يحنث من حلف ألا يأكل لبنًا بأكل مشتقاته كالزبد والسمن والجبن؟
Each school’s answer
In our wordsHanafi
Not stated in the sources
Maliki
Not stated in the sources
Shafi'i
Not stated in the sources
Hanbali
Not stated in the sources
The texts
١١٦٨ - مَسْأَلَةٌ وَمَنْ حَلَفَ أَنْ لَا يَأْكُلَ لَبَنًا لَمْ يَحْنَثْ بِأَكْلِ اللِّبَإِ وَلَا بِأَكْلِ الْعَقِيدِ، لَا الرَّائِبِ، وَلَا الزُّبْدِ، وَلَا السَّمْنِ، وَلَا الْمَخِيضِ، وَلَا الْمَيْسِ، وَلَا الْجُبْنِ - وَكَذَلِكَ الْقَوْلُ فِي الزُّبْدِ، وَالسَّمْنِ، وَسَائِرِ مَا ذَكَرْنَا لِاخْتِلَافِ أَسْمَاءِ كُلِّ ذَلِكَ. [مَسْأَلَةٌ حَلَفَ أَنْ لَا يَأْكُلَ خُبْزًا فَأَكَلَ كَعْكًا]
From the schools’ own books
Maliki
The sources give no view for it here.
Shafi'i
The sources give no view for it here.
Hanbali
The sources give no view for it here.
What is «in our words» is our standard wording; the books’ texts stay as they are.