Muwatta Malik, Book 43, Hadith 1582 (In-Book) ⓘ

Yahya related to me from Malik that he heard that Umar ibn Abd al-Aziz gave a decision that when a jew or christian was killed, his blood-money was half the blood-money of a free muslim. Malik said, "What is done in our community, is that a muslim is not killed for a kafir unless the muslim kills him by deceit. Then he is killed for it."

وَحَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عُمَرَ بْنَ عَبْدِ الْعَزِيزِ، قَضَى أَنَّ دِيَةَ الْيَهُودِيِّ، أَوِ النَّصْرَانِيِّ - إِذَا قُتِلَ أَحَدُهُمَا - مِثْلُ نِصْفِ دِيَةِ الْحُرِّ الْمُسْلِمِ ‏.‏ قَالَ مَالِكٌ الأَمْرُ عِنْدَنَا أَنْ لاَ يُقْتَلَ مُسْلِمٌ بِكَافِرٍ إِلاَّ أَنْ يَقْتُلَهُ مُسْلِمٌ قَتْلَ غِيْلَةٍ فَيُقْتَلُ بِهِ ‏.‏