All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
We previously mentioned the ruling on a person who does not pray in Fatwa 85264, so kindly refer to it.
As for the ideal way to advise one's father, it is as follows:
1- Dutifulness, obedience and kindness to your father will bring you closer to his heart, so that your advice will have a far-reaching effect.
2- Choosing the right situations and incidents when he may be more responsive, such as death of a relative, an accident or the like.
3- Seeking the help of those who are more likely to affect him, such a close friend, the Imaam of the mosque or any outspoken person who has a good approach when admonishing people.
4- Avoiding embarrassing him, hurting his feelings or provoking him.
5- Supplicating Allaah for him sincerely and earnestly, for Allaah The Almighty is The One to guide him.
Allaah Knows best.