Muslim Participation in a Funeral Prayer

Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) said,
"Whoever follows the funeral procession and offers the funeral prayer for it, will get a reward equal to one Qirat, and whoever attends it till burial, will get a reward equal to two Qirat.'' It was asked, "What are two Qirat?'' He (PBUH) replied, "Equal to two huge mountains.'' [Al-Bukhari and Muslim].
Commentary: Participation in a Muslim's funeral procession and prayer for him brings a Muslim a great reward - like the massiveness of a big mountain. And if he stays beside the grave till the burial takes place, the reward will become two-fold, that is, equaling the massiveness of two huge mountains. [Riyad-us-Saliheen: Chapter 155, Participation in Funeral Prayer and Procession - Number 929]

Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) said,
"Whosoever attends the funeral of a Muslim believing and hoping for the reward from Allah and remains with it until the prayer is offered over it and the burial is completed, he will return with a reward of two Qirat; each Qirat is equivalent to Mount Uhud; and whosoever offers his prayer over it and returns before its burial, he will come back with one Qirat.'' [Al-Bukhari].
Commentary: This Hadith explains that the only person who will earn the rewards for participating in the funeral prayer is the one who does it only to fulfill the Commands of Allah in order to seek His Pleasure. It will be denied to him in case his intention is based on social, political and family considerations. [Riyad-us-Saliheen: Chapter 155, Participation in Funeral Prayer and Procession - Number 930]