They were to keep the congregation of Israel clean and to help the unintentional manslayer to benefit from Jehovah’s mercy.
لِكَيْ يُحَافِظُوا عَلَى طَهَارَةِ ٱلْأُمَّةِ ،‏ وَيُسَاعِدُوا ٱلْقَاتِلَ سَهْوًا أَنْ يَسْتَفِيدَ مِنْ رَحْمَةِ يَهْوَهَ .‏