Sunan Abi Dawud 4317
سنن أبي داود#4317Sahihحَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، عَنْ مُحَمَّدِ بْنِ جَعْفَرٍ، عَنْ شُعْبَةَ، ك ف ر .
Shu’bah said in his version:“the letters k, f, r” (are on his forehead)
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Al-AlbaniSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih Muslim (2933)
In-book reference: 39:27