Musannaf Ibn Abi Shayba 33:840

Waki’ narrated to us, from Mis’ar, from ‘Abd al-Malik ibn Maysarah, from Muslim, from Suwayd ibn Jahbal, who said: Whoever says after the afternoon prayer (Asr), "There is no god but Allah, to Him belongs the dominion, and to Him belongs the praise, and He is capable of all things," they will fight on behalf of the one who says them until the same time the following day.