When the disease of Messenger of Allah ﷺ got aggravated, he covered his face with a Khamisa, but when he became short of breath, he would remove it from his face and say, "It is like that! May Allah curse the Jews Christians because they took the graves of their prophets as places of worship." By that he warned his follower of imitating them, by doing that which they did.
أَنَّ عَائِشَةَ وَعَبْدَ اللَّهِ بْنَ عَبَّاسٍ ؓ قَالاَ لَمَّا نَزَلَ بِرَسُولِ اللَّهِ ﷺ طَفِقَ يَطْرَحُ خَمِيصَةً لَهُ عَلَى وَجْهِهِ فَإِذَا اغْتَمَّ كَشَفَهَا عَنْ وَجْهِهِ فَقَالَ وَهْوَ كَذَلِكَ لَعْنَةُ اللَّهِ عَلَى الْيَهُودِ وَالنَّصَارَى اتَّخَذُوا قُبُورَ أَنْبِيَائِهِمْ مَسَاجِدَ يُحَذِّرُ مَا صَنَعُوا