Matthew Henry Commentary Joshua 20:1-6

"And Jehovah spake unto Joshua, saying, Speak to the children of Israel, saying, Assign you the cities of refuge, whereof I spake unto you by Moses, that the manslayer that killeth any person unwittingly [and] unawares may flee thither: and they shall be unto you for a refuge from the avenger of blood. And he shall flee unto one of those cities, and shall stand at the entrance of the gate of the city, and declare his cause in the ears of the elders of that city; and they shall take him into the city unto them, and give him a place, that he may dwell among them. And if the avenger of blood pursue after him, then they shall not deliver up the manslayer into his hand; because he smote his neighbor unawares, and hated him not beforetime. And he shall dwell in that city, until he stand before the congregation for judgment, until the death of the high priest that shall be in those days: then shall the manslayer return, and come unto his own city, and unto his own house, unto the city from whence he fled." — Joshua 20:1-6 (ASV)

When the Israelites were settled in their promised inheritance, they were reminded to set apart the cities of refuge, whose use and typical meaning have been explained (Numbers 35; Deuteronomy 19). God's spiritual Israel have, and always will have, in Christ and heaven, not only rest in which to repose, but also refuge in which to secure themselves. These cities were designed to typify the relief which the gospel provides for penitent sinners, and their protection from the curse of the law and the wrath of God, in our Lord Jesus, to whom believers flee for refuge (Hebrews 6:18).