Hisham bin Ishaq narrates from his father: A governor sent me to Abdullah bin Abbas (may Allah be pleased with them) so that I could ask him about the prayer of Istisqa (prayer for rain). He informed me: The Prophet Muhammad (peace and blessings be upon him) went out in ordinary clothes, expressing humility and modesty. He did not deliver a sermon like you people do. He performed two rak'ahs of prayer just as he used to perform on the occasion of Eid.
Hadith Referenceصحیح ابن حبان / كتاب الصلاة / 2862
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيحسن - «صحيح أبي داود» (1058).فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده حسن