Is it permissible to offer the obligatory or supererogatory Salah (Prayer) on behalf of one of the deceased's parents?
It is not permissible to offer Salah on behalf of another person; whether they are deceased or alive, or if it is obligatory or supererogatory, this is an act of Bid`ah (innovation in religion) as this has no legal evidence. The Prophet (peace be upon him) said:
Anyone who introduces anything into this matter of ours (Islam) that is not part of it will have it rejected.
In another wording:
Anyone who does an action which is not stated in this matter of ours (Islam) will have it rejected.
Agreed upon Hadith.
An exception to this ruling are the two Rak`ahs of circumambulation which may be performed by whoever performs Hajj and `Umrah on behalf of another person because it is a subsequent action of Hajj and `Umrah.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.