“Anyone who has set aside the law of Moses dies without mercy on the evidence of one or two witnesses.”
Here we have a not so gentle reminder of what happened to Israel if they failed to follow the law given by Moses. Punishment was swift and certain. The Israelites were not allowed to be wishy-washy. This is never clearer than in the treatment of Jesus by the Jewish leaders. Repeatedly they attempted to stone Him. Eventually, they talked Pilate into doing it for them. They did it, they said because of their law.
Keep in mind that the Hebrews letter is about a better covenant and a better covenant giver. The writer is continuing his comparison of the old and new covenants. This verse is about what happens to those that failed to follow the old covenant. Their judgment and punishment were without mercy. Lots of mercy under the law was available. There was even a mercy seat. But if a person sets the law aside, they lose the opportunity for mercy.
Task for Today: Think about what would have happened to you if you failed to keep the law under an ordinary man. Now think about the new law and the new lawgiver, the Son of God. Remember that mercy is for those keeping the covenant.