اَللَّهُمَّ اصْرَعْهُ

Allahum-mas ra'hu

O Allah! Cause him to fall down. Narrated by Anas bin Malik (RA): Allah's Messenger (ﷺ) arrived at Medina with Abu Bakr (RA), riding behind him on the same camel. Abu Bakr (RA) was an elderly man known to the people, while Allah's Messenger (ﷺ) was a youth that was unknown. Thus, if a man met Abu Bakr (RA), he would say, "O Abu Bakr! Who is this man in front of you?" Abu Bakr (RA) would say, "This man shows me the Way," One would think that Abu Bakr (RA) meant the road, while in fact, Abu Bakr (RA) meant the way of virtue and good. Then Abu Bakr (RA) looked behind and saw a horse-rider pursuing them. He said, "O Allah's Messenger (ﷺ)! This is a horse-rider pursuing us." The Prophet (ﷺ) looked behind and said - (The dua is mentioned above)

Reference: Bukhari: 3911