What is the supplication that a righteous child makes for his father so that his deeds are not cut off from this world?

Praying for one's father after his death involves asking for mercy and forgiveness, such as by saying: "O Allah, forgive my father, O Allah, have mercy on him." This is based on the Almighty's saying: "My Lord, have mercy upon them as they brought me up [when I was] small," and "My Lord, forgive me and my parents." This much is obligatory once in a lifetime, and anything beyond that is a bounty. One can also pray for him for the expansion and illumination of his grave, for entry into Paradise, and for salvation from the Hellfire.