This excerpt is taken from the book of Sheikh al-Islam Imam Ibn Taymiyyah, may Allah have mercy on him, Al-Jawab al-Bahir fi Zuwar al-Maqabir, translated by Sheikh Ataullah Saqib.
Travel for visitation is prohibited except for three mosques:
So whoever travels to a place other than the House of Allah and calls upon other than Allah there, he has performed his prayer and worship for other than Allah. Although the Messenger of Allah, peace be upon him, forbade traveling to any mosque other than the three mosques, unless there is a special reason to travel to it, except for the three mosques, because these three mosques were built by the Prophets, peace be upon them, and the general people were also invited to travel to them. So these three mosques have a special distinction that other mosques do not have. Therefore, traveling to any mosque other than these three mosques is unanimously not prescribed by the four Imams, and the Messenger of Allah, peace be upon him, forbade it.
So how can it be permissible to travel to such deceased whose graves have been made places of worship, idols, and fairs? And the irony is that they are considered partners with Allah and problem solvers, to the extent that most of them do not give Hajj to the House of Allah as much importance as they give to visiting their graves! Shirk and grave worship have been considered superior to Tawheed and worship of Allah, as is the case with the polytheists nowadays. Regarding shirk, Allah Almighty says:
إِنَّ اللَّهَ لَا يَغْفِرُ أَن يُشْرَكَ بِهِ وَيَغْفِرُ مَا دُونَ ذَٰلِكَ لِمَن يَشَاءُ ۚ وَمَن يُشْرِكْ بِاللَّهِ فَقَدْ ضَلَّ ضَلَالًا بَعِيدًا ﴿١١٦﴾ إِن يَدْعُونَ مِن دُونِهِ إِلَّا إِنَاثًا وَإِن يَدْعُونَ إِلَّا شَيْطَانًا مَّرِيدًا ﴿١١٧﴾ لَّعَنَهُ اللَّهُ
“Indeed, Allah does not forgive associating others with Him, but He forgives anything else of whoever He wills. Whoever associates others with Allah has gone far astray. They abandon Allah and make goddesses, and call upon the rebellious Satan whom Allah has cursed.”
Reference: (4-An-Nisa:116-118)
