[Ruling on Visiting the Grave of an Open Sinner and Supplicating for Him]

Answer—and Allah is the Guardian who grants success: There are two matters here—visitation and supplication.
As for supplicating for the father with mercy, forgiveness, and the rewards of the Hereafter, that is not permissible, due to His saying, Exalted is He: “It is not for the Prophet and those who have believed to ask forgiveness for the polytheists—even if they were relatives—after it has become clear to them that they are companions of the Blaze. And the request of Abraham for forgiveness for his father was only because of a promise he had made to him; but when it became clear to him that he was an enemy to Allah, he disassociated himself from him. Indeed, Abraham was most compassionate, forbearing.” [al-Tawbah:113–114]
As for visiting bereft of supplicating for the father, it is permissible for a purpose—such as fearing people’s blame were he to abandon the visit, or lest they say, “Look at this ‘religious’ person—his religiosity leads him to abandon visiting his own father,” which could cause people to be alienated from listening to him and accepting from him.
Furthermore, there is no doubt that visiting a disbelieving or sinful father during his lifetime is permissible, due to His sayings, Exalted is He: “Accompany them in the world with appropriate kindness,” [Luqmān:15] and “and to parents, good treatment.” [al-Baqarah:83] When the father dies, the default is that visiting remains permissible, by continuation of the prior ruling; nothing has appeared to us that would change this default. The verse only forbids seeking forgiveness for the enemies of Allah.
As for the report that the Prophet (May Allah bless him and his family and grant them peace) said, “I sought permission from my Lord to visit my mother’s grave … and He only permitted me for an hour,” or to that effect: it may be that this was at the beginning of the matter, for he had first forbidden visiting graves, then commanded it thereafter: “So—visit them, for they remind of the Hereafter.” This report is a solitary narration among the Sunnis, and it does not appear in Zaydī ḥadīth collections.
- Visiting graves for admonition and reflection is permissible absolutely, whether the occupants are Muslims or not. This may be indicated by His saying, Exalted is He, concerning Pharaoh: “So today We will save you in your body that you may be for those after you a sign.” [Yūnus:92] What appears to me to be prohibited is that one’s motive for visiting a grave be the person’s being an enemy of Allah; if that is the motive, then the visit is not permissible.
It is permissible to visit the grave of an open sinner or an oppressor for the purpose of taking heed—or to supplicate against him. It is related that Imām ʿIzz al-Dīn b. al-Ḥasan—peace be upon him—when he stood at the grave of Nashwān al-Ḥimyarī, recited lines of poetry noting his station in knowledge—were it not for hostility (against the Prophet’s Household).
As for visiting graves seeking reward and merit from Allah, this is only with respect to the righteous servants of Allah, for visiting them carries reward and merit. The Prophet (May Allah bless him and his family and grant them peace) used to visit the people of al-Baqīʿ, standing there for a long time and supplicating for them; and he visited the martyrs of Uḥud eight years after their killing and prayed over them as he would over the deceased.
Fāṭimah (peace be upon her) used to visit the grave of her uncle Ḥamzah b. ʿAbd al-Muṭṭalib at Uḥud every week.
Muslims, in all eras, have continued to visit the grave of the Prophet (May Allah bless him and his family and grant them peace), and the graves of the martyrs of Uḥud and the people of al-Baqīʿ. The adherents of all Islamic schools—both Shīʿī and Sunnī—seek nearness to Allah by visiting the Prophet (May Allah bless him and his family and grant them peace), the people of Uḥud, the people of al-Baqīʿ, and by visiting the graves of the Imāms, scholars, and devoted worshippers.
The first to denounce this was Ibn Taymiyyah; however, the Muslims paid no heed to his words nor acted upon them. Centuries later Muḥammad b. ʿAbd al-Wahhāb arose, and his standing grew strong; he revived Ibn Taymiyyah’s doctrine after his death. Allah is the One from Whom help is sought.
Source : Min Thimār al-ʿIlm wa al-Ḥikmah vol.1