Abu Dawud Book 8, Hadith Number 2554.
Chapter : Not known.
Narated By Samurah ibn Jundub : The Prophet (PBUH) named our cavalry “the Cavalry of Allah,” when we were struck with panic, and when panic overtook us, the Apostle of Allah (PBUH) commanded us to be united, to have patience and perseverance; and to be so when we fought.