Musannaf Ibn Abi Shayba 11:210

Muhammad ibn Bishr narrated to us, Abd al-Aziz ibn Umar narrated to us, Yazid ibn Yazid ibn Jabir narrated to me, from Makhul, from some of the companions of the Prophet, may Allah bless him and grant him peace, that supplication was recommended at the time of the falling of rain, the establishment of the prayer, and the meeting of the two ranks [in battle].