For it is commendable if someone endures pain, suffering unjustly, because of conscience toward God.
Endureth griefs ... This is a reference to the cruel, and even inhumane, sadistic treatment the slaves of that era often received from their masters.  They had no legal rights whatever; they could be beaten, maimed, burned with fire, or tortured in any manner that a wicked imagination might suggest.  Griefs indeed!  No class of people on earth ever suffered any more than the unhappy slaves who constituted the working capital of the ancient pagan world.  What an achievement for Christianity that such a scourge was finally banished.