Musnad Ahmad 293
Abul-Mukhariq Zuhair bin Salim narrated that `Umair bin Sa`d al-Ansari was appointed by `Umar as governor of Hims... and he mentioned the hadeeth `Umar said to Ka`b:
I am going to ask you about something, so do not hide it from me. [Ka`b said: By Allah I will not hide anything I know. ‘Umar said: What do you fear most for the ummah of Muhammad (ﷺ)? He said: Misleading leaders. `Umar said: The Messenger of Allah (ﷺ) told me about that in private and informed me of it.
حَدَّثَنَا عَبْدُ الْقُدُّوسِ بْنُ الْحَجَّاجِ، حَدَّثَنَا صَفْوَانُ، حَدَّثَنِي أَبُو الْمُخَارِقِ، زُهَيْرُ بْنُ سَالِمٍ أَنَّ عُمَيْرَ بْنَ سَعْدٍ الْأَنْصَارِيَّ، كَانَ وَلَّاهُ عُمَرُ حِمْصَ فَذَكَرَ الْحَدِيثَ قَالَ عُمَرُ يَعْنِي لِكَعْبٍ إِنِّي أَسْأَلُكَ عَنْ أَمْرٍ فَلَا تَكْتُمْنِي قَالَ وَاللَّهِ لَا أَكْتُمُكَ شَيْئًا أَعْلَمُهُ قَالَ مَا أَخْوَفُ شَيْءٍ تَخَوَّفُهُ عَلَى أُمَّةِ مُحَمَّدٍ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ أَئِمَّةً مُضِلِّينَ قَالَ عُمَرُ صَدَقْتَ قَدْ أَسَرَّ ذَلِكَ إِلَيَّ وَأَعْلَمَنِيهِ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ‏.‏