Muwatta Malik, Book 43, Hadith 1598 (In-Book) ⓘ

Yahya related to me from Malik from Abu'z-Zinad from Sulayman ibn Yasar that a slave was set free by one of the people on hajj and his master had abandoned the right to inherit from him. The ex-slave then killed a man from the Banu A'idh tribe. An A'idhi, the father of the slain man came to Umar ibn al-Khattab seeking the blood-money of his son. Umar said, "He has no blood-money." The A'idhi said, "What would you think if it had been my son who killed him?" Umar said, "Then you would pay his blood-money." He said, "He is then like the black and white Arqam snake. If it is left, it devours and if it is killed, it takes revenge."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ أَبِي الزِّنَادِ، عَنْ سُلَيْمَانَ بْنِ يَسَارٍ، أَنَّ سَائِبَةً، أَعْتَقَهُ بَعْضُ الْحُجَّاجِ فَقَتَلَ ابْنَ رَجُلٍ مِنْ بَنِي عَائِذٍ فَجَاءَ الْعَائِذِيُّ أَبُو الْمَقْتُولِ إِلَى عُمَرَ بْنِ الْخَطَّابِ يَطْلُبُ دِيَةَ ابْنِهِ فَقَالَ عُمَرُ لاَ دِيَةَ لَهُ ‏.‏ فَقَالَ الْعَائِذِيُّ أَرَأَيْتَ لَوْ قَتَلَهُ ابْنِي فَقَالَ عُمَرُ إِذًا تُخْرِجُونَ دِيَتَهُ فَقَالَ هُوَ إِذًا كَالأَرْقَمِ إِنْ يُتْرَكْ يَلْقَمْ وَإِنْ يُقْتَلْ يَنْقَمْ ‏.‏