12:4

In your struggle against that sin: That is, against the sin mentioned at Heb 12:1. (See study note.) Paul’s reasoning may here shift from the image of a footrace to that of a wrestling match or a boxing contest, with sin being portrayed as the opponent. (Compare 1Co 9:26, where Paul also uses both word pictures.) In the Greco-Roman world, those fights were dangerous, at times even deadly. A fighter who was locked in such a struggle might be knocked down by his opponent, but he could not afford to give in to discouragement; he needed to get up, all the more determined to win. In a similar way, a Christian faces tests and hard blows, but rather than give up, he needs to put up a hard fight for his faith.​—2Ti 4:7; Heb 12:3; Jude 3.

you have never yet resisted to the point of having your blood shed: Decades earlier, some of the first Christians in Jerusalem had been put to death for their faith. (Ac 7:59–8:3; 12:2) And many of those whom Paul is addressing had endured opposition and persecution. (Heb 10:32-34) Still, it seems that the majority had accepted Christianity during a relatively peaceful period. Even so, some were growing weary. (Heb 12:3) To strengthen their determination to endure whatever might yet come, Paul goes on to explain that tests of faith are a necessary part of a Christian’s discipline, or training.​—Heb 12:7-13; see also Heb 12:5 and study note.