Musannaf Ibn Abi Shayba 3:5885

Jarir narrated to us, from Mughira, from Ibrahim, regarding the saying of the Exalted: "But if you fear, then [pray] on foot or riding." He said: If the prayer time arrives while you are in pursuit, then gesture [to pray] in whichever direction you are facing, and make the prostration lower than the bowing.