Sunan an-Nasa'i 4744
It was narrated that Ash-Sha'bi said:
"I heard Abu Juhaifah say: 'We asked 'Ali: "Do you have anything from the Messenger of Allah apart from the Qur'an?" He said:  "No, by the One who splits the seeds and creates the soul, unless Allah gives a slave understanding of His Book, or except this sheet." I said: "What is in the sheet?" He said: "In it are (the regulations concerning) blood money and the freeing of captives and (the rule) that no Muslim should be killed for killing a disbeliever."
أَخْبَرَنَا مُحَمَّدُ بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ مُطَرِّفِ بْنِ طَرِيفٍ، عَنِ الشَّعْبِيِّ، قَالَ سَمِعْتُ أَبَا جُحَيْفَةَ، يَقُولُ سَأَلْنَا عَلِيًّا فَقُلْنَا هَلْ عِنْدَكُمْ مِنْ رَسُولِ اللَّهِ صلى الله عليه وسلم شَىْءٌ سِوَى الْقُرْآنِ فَقَالَ لاَ وَالَّذِي فَلَقَ الْحَبَّةَ وَبَرَأَ النَّسَمَةَ إِلاَّ أَنْ يُعْطِيَ اللَّهُ عَزَّ وَجَلَّ عَبْدًا فَهْمًا فِي كِتَابِهِ أَوْ مَا فِي هَذِهِ الصَّحِيفَةِ ‏.‏ قُلْتُ وَمَا فِي الصَّحِيفَةِ قَالَ فِيهَا ‏
"‏ الْعَقْلُ وَفِكَاكُ الأَسِيرِ وَأَنْ لاَ يُقْتَلَ مُسْلِمٌ بِكَافِرٍ ‏"‏ ‏.‏