Prophet's Mosque and Hajj

TLDR: Sunnis, during Hajj, also make a pilgrimage to the prophet's tomb and claim that this is the second Holy Shrine when the Quran only acknowledges the Kaaba as the only Holy Shrine for the Muslims.

God commands the believers to perform Hajj (pilgrimage) to His Sacred Shrine to worship God alone, yet most pilgrims will also include a stop to Medina to pray at the Al-Masjid an-Nabawi (Mosque of the Prophet), which contains the tomb of prophet Muhammad. So this simple act that is supposed to be devoted to God alone has now been corrupted by adding a partner with God. Ironically, in a series of very famous Hadith, the prophet condemned the Christians and Jews for doing such a thing.

Narrated Aisha andAbdullah bin `Abbas: When the last moment of the life of Allah's Messenger (ﷺ) came he started putting his 'Khamisa' on his face and when he felt hot and short of breath, he took it off his face and said, "May Allah curse the Jews and Christians for they built the places of worship at the graves of their Prophets." The Prophet (ﷺ) was warning (Muslims) of what those had done.

حَدَّثَنَا أَبُو الْيَمَانِ، قَالَ أَخْبَرَنَا شُعَيْبٌ، عَنِ الزُّهْرِيِّ، أَخْبَرَنِي عُبَيْدُ اللَّهِ بْنُ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، أَنَّ عَائِشَةَ، وَعَبْدَ اللَّهِ بْنَ عَبَّاسٍ، قَالاَ لَمَّا نَزَلَ بِرَسُولِ اللَّهِ صلى الله عليه وسلم طَفِقَ يَطْرَحُ خَمِيصَةً لَهُ عَلَى وَجْهِهِ، فَإِذَا اغْتَمَّ بِهَا كَشَفَهَا عَنْ وَجْهِهِ، فَقَالَ وَهْوَ كَذَلِكَ ‏ "‏ لَعْنَةُ اللَّهِ عَلَى الْيَهُودِ وَالنَّصَارَى اتَّخَذُوا قُبُورَ أَنْبِيَائِهِمْ مَسَاجِدَ ‏"‏‏.‏ يُحَذِّرُ مَا صَنَعُوا‏.‏

Sahih al-Bukhari 435, 436 https://sunnah.com/bukhari:435

Ironically, Abd al-Malik's son, al-Waleed I, expanded the Mosque of the Prophet around 706 CE so that the prophet's tomb, as well as that of the first two caliphs Abu Bakr (r. 632-634) and Umar (r. 634-644) would be encompassed inside the mosque.