Narrated Ibn `Abbas:
Regarding the Verse: "Verily! The worst of beasts in the Sight of Allah are the deaf and the dumb---- those who understand not." (8.22) (The people referred to here) were some persons from the tribe of Bani `Abd-Addar.
USC-MSA web (English) reference: Vol. 6, Book 60, Hadith 169
Arabic reference: Book 65, Hadith 4646