Musnad Ahmad 498:5

Hajjaj ibn Muhammad narrated to us, Shu'bah informed me, from 'Amr ibn Dinar, from 'Amr ibn Aws, from a man who narrated to him from the Mu'adhdhin (caller to prayer) of the Prophet, may Allah bless him and grant him peace, who said: The caller of the Prophet, may Allah bless him and grant him peace, called out on a rainy day: "Pray in your dwellings."