Two great reciters of the Qur’ān, Imām Yazīdī and Imam Kisā’ī were once in the presence of Hārūn Ar-Rashīd, when the time for ṣalāh arrived. They decided that Imam Kisā’ī would lead the ṣalāh. During the course of his recitation of Sūrah al-Kāfirūn, he stammered for a moment. When they had completed, Imām Yazīdī remarked, “The Qāri of Kūfa stammered while reciting a simple Sūrah like this!”
When the time arrived for the next Ṣalāh, Imām Yazīdī was ushered forward to lead the prayer. During his recitation of Sūrah Fātiḥah, he stammered. When he had completed, he remarked, احفظ لسانك لا يقول فتبلى … إن البلاء موكل بالمنطق “Guard your tongue so that it does not speak a word that will cause you distress. Distress is a result of speech.”
One who is hasty to pass remarks at the mistakes of others, is often put to shame by his own mistakes.
[Tārīkh Baghdād, volume 13, page 351; Tārīkhul Islām Dhahabī || Pearls from the Path, volume 2, Page 118-119]