Did it come from the Prophet (peace and blessings be upon him) that the congregation raises their hands for supplication after the prayer for rain sermon?

Question:
Yes. He says: Honorable Shaykh, may Allah grant you success, did it come from the Prophet (peace and blessings be upon him) that the congregation, after the prayer for rain sermon, stand with their hands raised and supplicate for a long time? When the Prophet (peace and blessings be upon him) finished his supplication, he turned toward the qiblah, turned his cloak (peace and blessings be upon him) while facing the qiblah, and raised his hands to supplicate.

Answer:
And the Muslims did as he did; they turned their cloaks, raised their hands, and supplicated to Allah facing the qiblah, following the Prophet (peace and blessings be upon him). This is a good thing.