Numbers 35

“Speak to the children of Israel, and say to them: ‘When you cross the Jordan into the land of Canaan,  then you shall appoint cities to be cities of refuge for you, that the manslayer who kills any person accidentally may flee there.'" vv.10-11

Read chapter 35
Cities of refuge.  A place that provided protection for one who killed someone unintentionally.  The murderer may flee to one of these six cities till stood trial.  Even if they're acquitted they must then still stay and live in the city of refuge till the high priest dies.  So only by the death of Jesus our High Priest are sinners liberated.  These cities had to be easy to get to so we see three placed on each side of Jordan River.  Just like us when we sin accidentally or knowingly with repentance in our heart are we to RUN to Jesus who's our city of refuge.  If murder accidentally happens today one still has to stand trail and are in a hold facility until acquitted or receive their penalty.

"The surprising thing when we look through the scriptures is that we can find no actual example recorded of someone actually using the cities of refuge. 

Yet despite this we see the appointment of these Cities was an act of grace and mercy which foreshadowed those characteristics manifested by the Lord.

Unfortunately, in the symbolic application of the Cities of Refuge, comparatively few take heed of the offer of grace in Christ Jesus, and so are destroyed by the Avenger of blood, sin in the flesh." (bridgetothebible.com)