Rashi on Numbers
מגאל — [AND THE CITIES SHALL BE UNTO YOU AS A REFUGE] מגאל — i.e. as a refuge on account of the avenger of blood, — he who is the near relative of the murdered man.
Rabbeinu Bahya
למקלט מגואל, “as a refuge from the avenger.” The reference is to a family member of the slain person who would act as his avenger.
Siftei Chakhamim
Against the blood redeemer. Meaning that מגואל ["from the avenger"] refers to the blood redeemer. Rashi continues to explain which person is termed the blood redeemer, given the name “redeemer” could refer either to the redeemer of the murderer or to the redeemer of the victim. Therefore Rashi explains that he is a kinsman of the victim.