Jami At Tirmidhi
557
Sahih+2

Umair, the freed slave of Abi Al-Lahm narrated from Abi Al-Lahm that :he saw the Messenger of Allah at Ahjar Az-Zait, supplicating for rain, and he was raising his hands in supplication

SahihAhmad Muhammad Shakir
SahihAl-Albani