He saw the Messenger of Allah ﷺ at Ahjar al-Zayt praying for rain, with his palms turned upward as he made supplication.
حدثنا قتيبة حدثنا الليث بن سعد عن خالد بن يزيد عن سعيد بن أبي هلال عن يزيد بن عبد الله عن عمير مولى آبي اللحم
أنه رأى رسول الله ﷺ عند أحجار الزيت يستسقي وهو مقنع بكفيه يدعو
Sourcing, sahih. Nasai transmitted it, 3/158, 159, 1515 (Istisqa, Chapter, How is it raised), Abu Dawud, no. 1168, 1172, from Qutayba, with the same wording. Hakim declared it sahih, 1/535, as did Dhahabi. The hadith has corroborating narrations found in Ibn Hibban, no. 601, 602, and others.