Sahih al-Bukhari 5815, 5816Book 77, Hadith 33
حَدَّثَنِي يَحْيَى بْنُ بُكَيْرٍ، حَدَّثَنَا اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ ابْنِ شِهَابٍ، قَالَ أَخْبَرَنِي عُبَيْدُ اللَّهِ بْنُ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، أَنَّ عَائِشَةَ، وَعَبْدَ اللَّهِ بْنَ عَبَّاسٍ، رضى الله عنهم قَالاَ لَمَّا نَزَلَ بِرَسُولِ اللَّهِ صلى الله عليه وسلم 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.
When the disease of Allah's Messenger (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.