Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1206
Abu Ma'mar reported: There was an Amir in Mecca who pronounced taslim twice. Abdullah said: Where did he get this sunnah? Al-Hakam said: There is a hadith to the effect that the Messenger of Allah (may peace be upon him) did like It.