What can the family of the deceased, who abandoned prayer, do to alleviate his suffering in the grave?

"Whoever dies having abandoned prayer, denying its obligation after being informed, is, by consensus, an apostate disbeliever. Such a person is not eligible for intercession, seeking forgiveness, or supplication, based on the Almighty's saying: 'It is not for the Prophet and those who have believed to ask forgiveness for polytheists, even if they were relatives, after it has become clear to them that they are companions of Hellfire.' And based on the Prophet's saying: 'I asked my Lord for permission to seek forgiveness for my mother, but He did not grant it. So I asked Him for permission to visit her, and He granted it.'

As for whoever abandons prayer while affirming its obligation, whether intentionally or out of laziness, and dies without repenting, they are an apostate disbeliever, according to the more correct of the two scholarly opinions, and this is the view of the majority of the Salaf. Such a person is not eligible for intercession, seeking forgiveness, or supplication, due to the absolute nature of the hadiths, such as: 'The covenant between us and them is prayer; whoever abandons it has disbelieved,' and 'Between a man and disbelief and polytheism is the abandonment of prayer.' And because the Companions unanimously agreed on the disbelief of one who abandons prayer.

Some scholars are of the view that one who abandons prayer out of laziness, without denying its obligation, commits practical disbelief that does not expel them from Islam, and they are eligible for intercession and seeking forgiveness. However, this is a weak opinion."