The mitzvot of Masei

The commandment on Israel to give cities within which the Levites may dwell, and they shelter

Positive · Numbers 35:2

The tribe of Levi is the choicest of the tribes, set apart for the service of God's House, and it has no share in fields and vineyards, but it does need cities to live in. Because of their high standing, their land was chosen to shelter one who killed by accident, in the hope that their sanctified land would atone for him. Moreover, since they are people of fine character and wisdom, they would not hate the killer who fled to them or harm him, even if he had killed one of their own loved ones.

To not kill someone liable before he is brought to justice

Negative · Numbers 35:12

Capital cases are a very grave matter that demands great precision, and the judges were commanded to seek every merit that might save the accused, though without bending the law. Therefore one who is liable may not be put to death until he stands before a court, and even the witnesses who saw the act with their own eyes do not judge him, for one who saw the thing himself will not be able to search for his merit.

The commandment on the court to send one who smites a soul inadvertently from his city to the cities of refuge and upon the killer himself to go there

Positive · Numbers 35:25

The sin of murder is exceedingly grave, for it brings ruin to the world. So it is fitting that one who killed, even by accident, should feel the great calamity that came about through him in the pain of exile, which is almost like the pain of death - parting from his loved ones and his homeland and living among strangers. Moreover, in the city of refuge he is saved from the blood-avenger, since he acted unintentionally, and the relatives of the one killed do not see him constantly before their eyes in the place where the harm occurred.

That the witness not issue a ruling in the case that he is testifying about in capital punishments

Negative · Numbers 35:30

Capital cases require great precision, and the court is obliged to seek every merit that might save the accused. A witness who saw the act with his own eyes has already concluded in his heart that the accused is guilty and will not be able to search for his merit, so he may not be among the judges in that case.

Not to take ransom to save the murderer from the death penalty

Negative · Numbers 35:31

The root of the mitzvah is well known - if it were permitted to accept ransom from a murderer, anyone greater and richer than his fellow would kill him in a moment of anger and pay his ransom. Then every man's sword would be against his brother, and society would be destroyed.

Not to take ransom from one liable for exile to exempt him from exile

Negative · Numbers 35:32

Just as ransom is not taken from a deliberate murderer, so it is not taken from one who killed by accident to exempt him from exile. If a person could buy his exemption with money, the rich would treat human life lightly, and exile would not achieve its purpose, that the killer feel sorrow for the calamity that came about through him.