In Islam, there is nothing wrong that a Muslim visits the grave of a saint or a Wali, but a Muslim has to stick to the Islamic rulings in this regard. He is not permitted to not ask, pray, or supplicate to any one other than Allah.
Sheikh `Atiyyah Saqr, former head of Al-Azhar Fatwa Committee, states the following: “It is well known that when one loves somebody one loves all that is related to him. Such an innate human characteristic is not opposed by religion; rather, it is guided in two ways. The first is choosing those who deserve that love and veneration and the second is not violating the principles of religion in expressing this love or in any of its consequences. Seeking the blessings of pious people or saints is not forbidden under Islam but it might have some features that are against religion such as:
1. Going round the grave is blameworthy because it is an imitation of circumambulating the Ka`bah.
2. Seeking blessings by touching or kissing the grave and the like. Imam Al-Ghazali states that touching and kissing graves is not stated in the Sunnah and it is better to stand at a distance from the grave.
3. When one performs du`a’ (supplications) at graves, one must direct such du`a’ to Allah alone for He alone is capable of granting help and warding off harm.
It is forbidden to direct the du`a’ to or seek the help of the one in the grave however venerated he may be. Moreover, performing du`a’ at his grave is not better or more likely to be answered than doing it elsewhere. Ibn Taymiyyah was among those who expressed such opinion. He says: ‘Making supplications (du`a’) at graves of the righteous thinking that the supplications are more likely to be answered than in any other place, is a practice that had never been done by the Prophet (peace and blessings be upon him) or any of his Companions, their successors, or the Imams of Islam and has never been mentioned or recommended by any of the righteous scholars.’”