1. Bilal Al Habashi said to Umar Ibn Khattab :
"We know the time better than you do (Umar), and you are even more misguided than your domesticated donkey"
[Tarikh Madinat Dimashq by Ibn Asakir, Volume 10 page 474]
2. Hudhayfa bin al Yaman :
"I swear By Allah that you (Umar ibn Khattab) are a Fool"
Isnad is SAHIH
[Musanaf Abd Al Razaq Al Sanani, Volume 7, page 322, No 17358]