Abu Dawud Book 30, Hadith Number 4252.
Chapter : Restraining the tongue during the period of commotion.
Narated By Abdullah ibn Amr ibn al-‘As : The Prophet (PBUH) said: There will be civil strife which wipe out the Arabs, and their slain will go to Hell. During it the tongue will be more severe than blows of the sword.
Abu Dawud said: Al-Thawri transmitted it from Laith, from Tawus on the authority of al-A’jam.