Sayyiduna Ibn Abbas (may Allah be pleased with them both), in explaining "Legal retribution (qisas) is prescribed for you in the case of those killed" [Surah al-Baqarah: 178] to the end of the verse, said: Legal retribution alone was obligatory upon the Children of Israel, and for you the concession of blood money has been granted. "But whoever is pardoned something by his brother, then let there be a following up with what is fair and payment to him with excellence" [Surah al-Baqarah: 178] means: when, in deliberate killing, the heir of the slain agrees to blood money, then pay the blood money with excellence. "That is an alleviation from your Lord and a mercy. So whoever transgresses after that will have a painful punishment" [Surah al-Baqarah: 178] means: in comparison with the Children of Israel.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16036