Sahih Muslim 2512
صحيح مسلم#2512Sahihوَحَدَّثَنِيهِ مُحَمَّدُ بْنُ حَاتِمٍ، حَدَّثَنَا ابْنُ مَهْدِيٍّ، عَنْ سُفْيَانَ، عَنِ الأَسْوَدِ بْنِ قَيْسٍ، بِهَذَا الإِسْنَادِ وَلَمْ يَذْكُرْ لِلشَّهْرِ الثَّانِي ثَلاَثِينَ .
This hadith has been narrated on the authority of Aswad b. Qais with the same chain of transmitters, but herein no mention has been made of the other month (consisting of) thirty days
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:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 13:18