Torah Temimah points to Makos 10a (cities of refuge must be of intermediate size, with water, markets, and population, and without traps that would attract the blood-avenger).
English: It was taught: Cities of refuge are made only of intermediate-sized towns; they are settled only in a place of water, markets and population; and one does not spread nets or hang ropes in them, so that the foot of the blood-avenger will not be found there.
On the daf / in context: “Va-chai” requires that the exile be able to live a normal life, not merely hide; therefore the city must support ordinary commerce and safety.
Type of Learning
Diyuk of “va-chai” as requiring conditions for ordinary life in the city of refuge.
What Is Learned
A city of refuge must be large enough and well-supplied to sustain life, yet not so large or so set with traps that the blood-avenger is drawn there.