Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 2069
Thauban, the freed slave of the Messenger of Allah (may peace be upon him) reported Allah's Messenger (may peace be upon him) as saying: He who offered prayer for the dead, for him is the reward of one qirat, and he who attended its burial, he would have two qirats as his reward. And qirat is equivalent to Uhud.