Deuteronomy 19:8

And if the LORD thy God enlarge thy coast, as he hath sworn unto thy fathers, and give thee all the land which he promised to give unto thy fathers;

Deuteronomy 19:8 belongs to the Mosaic law of the cities of refuge. It presents the enlargement of Israel's territory and the possession of all the land promised to the ancestors as a conditional future gift from God, grounded in His oath to those ancestors. It directs establishing cities of refuge after that enlargement, when God has given the enlarged territory He swore and promised to give. That law mitigated the Hebrew custom of the avenger, which authorized and even required the next of kin of a murdered person to kill the murderer and was too deeply rooted to be suddenly abolished.

The cities let a homicide escape private vengeance and claim a fair trial. Elders at the city gate admitted the fugitive, while a regular trial before a higher court was held later when witnesses and accusers could appear. The provision did not grant escape from the legal consequences of murder, for it protected the manslayer from a relative's private vengeance only until he received a fair trial and the case had to be judged. A killing proved accidental was not punished.

The cities of refuge were places of safety where people could hide from any danger that might threaten the community. That provision calls for securing a refuge for Jews who accept Christ and must leave their countrymen under bitter persecution. There they are given work and at the same time trained to become workers for others.