Verses 1-3 – These cities were to be strategically located so that they would be accessible to anyone anywhere in the land. People could escape to these places if they had unintentionally killed someone (manslaughter).
Verses 3-11 – God had an answer for those who killed innocently or accidentally. They could run to these cities until they had a trial and could escape someone coming after them to avenge the one killed. Revenge for murder was not only permitted by the law but fully authorized (Numbers 35:16-21).
Verses 11-12 – For the murderer there was no place of refuse or safety. From the beginning of history, the penalty for murder was capital punishment. The “Avenger of blood” was the nearest male relative to the person killed. He acted as the family protector (Numbers 35:19).
Verse 15 – To prevent a miscarriage of justice, the law required the testimony of two or three witnesses.
Verse 16-20 – If only our justice system would take a hint of what true justice is. One person could not stand against another in a court of law; if you falsely accused someone of a crime and it was found out they had lied, then the punishment that was intended for the accused was placed on the accuser. This would certainly clear the courts of frivolous lawsuits.
Verse 21 – The principle was that the punishment was to fit the crime. This tit for tat of the law was not always followed (Exodus 22:21; Numbers 35:31).