Two Rak’ah of Voluntary Prayer
Abu Huraira (may Allaah be pleased with him) said: the Messenger of Allaah (sallahAllaahu alayhi wasallam) passed by a recently-dug grave and said:
“Two brief Rak’ah –which you regard as insignificant and you pray them as optional prayer-, they [the two rak’ah] increase him – while pointing to the grave – in deeds what is more beloved to him than the rest of your Dunya [world].” 
Glorified is Allaah, the hadeeth shows the importance of one’s deeds and that the person in his grave will value that he had prayed just two rak’ah, and they will be more valuable to him then the whole world and its posessions.
1. Silsilah as-Saheeha: 1388