ENOfficial
Abu Huraira reported God's Messenger as saying, "Every sermon which does not contain a tashahhud is like a hand cut off.” Tirmidhi transmitted it, saying this is a hasan gharib tradition.
Source: sunnah.com
Other translations
Arabic
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
sunnah.com