Sahih Bukhari, Chapter: Prayers (Salat)

I asked Jabir bin 'Abdullah about praying in a single garment. He said, "I travelled with the Prophet during some of his journeys, and I came to him at night for some purpose and I found him praying. At that time, I was wearing a single garment with which I covered my shoulders and prayed by his side. When he finished the prayer, he asked, 'O Jabir! What has brought you here?' I told him what I wanted. When I finished, he asked, 'O Jabir! What is this garment which I have seen and with which you covered your shoulders?' I replied, 'It is a (tight) garment.' He said, 'If the garment is large enough, wrap it round the body (covering the shoulders) and if it is tight (too short) then use it as an Izar (tie it around your waist only.)' "