Maliks Muwatta Book 13, Hadith Number 2.
Section : About Asking for Rain.
Yahya related to me from Malik from Yahya ibn Said from Amr ibn Shuayb that the Messenger of Allah, may Allah bless him and grant him peace, said, when he asked for rain, “O Allah, give water to Your slaves and Your animals, and spread Your mercy, and give life to Your dead land.”