It is narrated from Abu Ishaq that Abdullah bin Yazid al-Ansari (may Allah be pleased with him) went out to supplicate for rain, and he had seen the Prophet (peace and blessings be upon him). Among those who went out with him were al-Bara' bin Azib and Zayd bin Arqam (may Allah be pleased with them both). Abu Ishaq said: I too was with him that day. He stood on his feet, without a pulpit. Then he supplicated for rain and sought forgiveness, then he led us in two rak'ahs while we were behind him, reciting aloud in them; and he gave neither the adhan nor the iqamah. Imam Bukhari (may Allah have mercy on him) narrated this report in his Sahih from Abu Nu'aym. In what al-Thawri narrated from Abu Ishaq, he said: He delivered a sermon, then prayed. And in what Shu'bah narrated, it says that he prayed two rak'ahs, then supplicated.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الاستسقاء / 6410