On his death-bed Messenger of Allah ﷺ put a sheet over his-face and when he felt hot, he would remove it from his face. When in that state (of putting and removing the sheet) he said, "May Allah's Curse be on the Jews and the Christians for they build places of worship at the graves of their prophets." (By that) he intended to warn (the Muslim) from what they (i.e. Jews and Christians) had done. (Using translation from Bukhārī 3453)  

أَنَّ عَائِشَةَ وَابْنَ عَبَّاسٍ قَالَا لَمَّا نَزَلَ بِرَسُولِ اللهِ ﷺ طَفِقَ يَطْرَحُ خَمِيصَةً لَهُ عَلَى وَجْهِهِ فَإِذَا اغْتَمَّ كَشَفَهَا عَنْ وَجْهِهِ وَقَالَ وَهُوَ كَذَلِكَ «لَعْنَةُ اللهِ عَلَى الْيَهُودِ وَالنَّصَارَى اتَّخَذُوا قُبُورَ أَنْبِيَائِهِمْ مَسَاجِدَ»  

Um Habiba and Um Salama mentioned about a church they had seen in Ethiopia in which there were pictures. They told the Prophet ﷺ about it, on which he said, "If any religious man dies amongst those people they would build a place of worship at his grave and make these pictures in it. They will be the worst creature in the sight of Allah on the Day of Resurrection." (Using translation from Bukhārī 427)  

أَنَّ أُمَّ حَبِيبَةَ وَأَمَّ سَلَمَةَ ذَكَرَتَا كَنِيسَةً رَأَيْنَهَا بِالْحَبَشَةِ فِيهَا تَصَاوِيرُ فَقَالَ رَسُولُ اللهِ ﷺ «إِنَّ أُولَئِكَ إِذَا كَانَ فِيهِمُ الرَّجُلَ الصَّالِحُ فَمَاتَ بَنَوْا عَلَى قَبْرِهِ مَسْجِدًا وَصَوَّرُوا تِلْكَ الصُّوَرَ أُولَئِكَ شِرَارُ الْخَلْقِ عِنْدَ اللهِ يَوْمَ الْقِيَامَةِ»