Musnad Ahmad 1153:1846

Hajjaj narrated to us, he said: Shareek informed us, from al-Miqdam ibn Shurayh, from his father, from Aisha, who said: When the Prophet, peace and blessings of Allah be upon him, saw a formation in the sky—a cloud or wind—he would face it from wherever it was. And if he was in prayer, he would seek refuge in Allah, the Almighty and Majestic, from its evil. Then, when it rained, he would say: "O Allah, a beneficial downpour."