‘Abdallah b. Zaid said God's Messenger took the people out to the place of prayer and prayed for rain. He led them in two rak'as in the course of which he recited from the Qur'an in a loud voice. He faced the qibla making supplication, raised his hands and turned round his cloak when he faced the qibla.
We went out with God’s Messenger from Mecca making for Medina, and when we were near ‘Azwaza’* he alighted, then raised his hands and made supplication to God for a time, after which he prostrated himself, remaining a long time in prostration. Then he stood up and raised his hands for a time, after which he prostrated himself, remaining a long time in prostration. Then he stood up and raised his hands for a time, after which he prostrated himself. He then said, “I begged my Lord and made intercession for my people, and He gave me a third of my people, so I prostrated myself in gratitude to my Lord. Then I raised my head and begged my Lord for my people and He gave me a third of my people, so I prostrated myself in gratitude to my Lord. Then I raised my head and begged my Lord for my people and He gave me the last third, so I prostrated myself in gratitude to my Lord.”
*The name is spelt either as here with the alif mamduda, or with the alif maqsura (i.e. Azwaza). The reference is to a pass in the hills.
Anas said the Prophet was not accustomed to raise his hands in any supplication he made except when praying for rain. He would then raise them high enough for the whiteness under his armpits to be visible.