Hadithcore
Mishkat al-Masabih, 269

Ziyad b. Hudair said that ‘Umar asked him whether he knew what demolishes Islam, and that when he replied that he did not, he said, "The slip of a learned man, the disputation of a hypocrite about the Book, and the rule of <i>imams</i> who lead men astray.” Darimi transmitted it.

وَعَن زِيَاد بن حدير قَالَ: قَالَ لِي عُمَرُ: هَلْ تَعْرِفُ مَا يَهْدِمُ الْإِسْلَامَ؟ قَالَ: قُلْتُ: لَا. قَالَ: يَهْدِمُهُ زَلَّةُ الْعَالِمِ وَجِدَالُ الْمُنَافِقِ بِالْكِتَابِ وَحُكْمُ الْأَئِمَّةِ المضلين ". رَوَاهُ الدِّرَامِي

References1 variant
In-Book Reference
Book 2, Hadith 65