Deuteronomy 19:6

Overview - Deuteronomy 19
The cities of refuge.
The privilege thereof for the manslayer.
14 The land-mark is not to be removed.
15 Two witnesses at the least are required.
16 The punishment of a false witness.
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Deuteronomy 19:6  (King James Version)
Lest the avenger of the blood pursue the slayer, while his heart is hot, and overtake him, because the way is long, and slay him; whereas he was not worthy of death, inasmuch as he hated him not in time past.

the avenger
Numbers 35:12 ; Joshua 20:5 ; 2 Samuel 14:7

slay him
Hebrew smite him in life. not worthy.
21:22 Jeremiah 26:15 Jeremiah 26:16

in time past
Hebrew from yesterday the third day.