Walid bin Uqba, who was then governor of Madinah, sent me to Ibn Abbas to ask him how the Messenger of Allah ﷺ prayed for rain. So I went to him.Ibn Abbas said, "The Messenger of Allah ﷺ went out dressed plainly, humble and imploring, until he reached the prayer ground. He did not deliver a sermon like this sermon of yours. Rather, he continued in supplication, humble entreaty, and takbir, and he prayed two units of prayer just as he used to pray on Eid."
حدثنا محمود بن غيلان حدثنا وكيع عن سفيان عن هشام بن إسحق بن عبد الله بن كنانة عن أبيه فذكر نحوه وزاد فيه متخشعا
[Hasan]. Ibn Majah reported it in Iqamat al-Salawat, Chapter on What Has Been Reported Regarding the Prayer for Rain, hadith no. 1266, from the hadith of Waki with the same chain. See also the previous hadith.