Hadithcore
Mishkat al-Masabih, 3150

Abu Huraira reported God's Messenger as saying, "Every sermon which does not contain a <i>tashahhud</i> is like a hand cut off.” Tirmidhi transmitted it, saying this is a <i>hasan gharib</i> tradition.

وَعَنْ أَبِي هُرَيْرَةَ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «كُلُّ خُطْبَةٍ لَيْسَ فِيهَا تَشَهُّدٌ فَهِيَ كَالْيَدِ الْجَذْمَاءِ» . رَوَاهُ التِّرْمِذِيُّ وَقَالَ: هَذَا حَدِيثٌ حَسَنٌ غَرِيبٌ

References1 variant
In-Book Reference
Book 13, Hadith 70