Imam Malik's Muwatta, Chapter: Prayer in Congregation

Yahya related to me from Malik that he had heard from Jabir ibn Abdullah that the Messenger of Allah, may Allah bless him and grant him peace, said, "Let anyone who cannot find two garments pray in one garment and wrap himself in it, and if the garment is short, let him wrap it around his waist." Malik said, "In my view it is preferable for someone who prays in a single shirt to put a garment or a turban over his shoulders."