Hisham bin Ishaq bin Abdullah bin Kinanah narrates from his father that one of the governors sent me to Sayyiduna Ibn Abbas (may Allah be pleased with them both) to ask him about the rain prayer. Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: What prevented him from asking me himself? Then he said: He (peace and blessings be upon him) went out humbly, with submissiveness and lowliness, entreating earnestly and walking gently. Then he (peace and blessings be upon him) led two rak'ahs as he used to lead the Eid prayer, and he (peace and blessings be upon him) did not deliver a sermon like your sermon.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الاستسقاء / 6387