Sahih Bukhari Volume 5, Book 64, Hadith 4446

وَأَخْبَرَنِي 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 وَهْوَ كَذَلِكَ يَقُولُ ‏"‏ لَعْنَةُ اللَّهِ عَلَى الْيَهُودِ وَالنَّصَارَى، اتَّخَذُوا قُبُورَ أَنْبِيَائِهِمْ مَسَاجِدَ ‏"‏‏.‏ يُحَذِّرُ مَا صَنَعُوا‏.‏

'Aisha and 'Abdullah bin 'Abbas said, "When Allah's Apostle became ill seriously, he started covering his face with his woollen sheet, and when he felt short of breath, he removed it from hi; face and said, 'That is so! Allah's (curse be on the Jews and the Christians, as they took the graves of their prophets as (places of worship),' intending to warn (the Muslims) of what they had done."