The power of the covenant assures that Jehovah will accept a repentant Israel. There are some, however, who may assume that since they are of the house of Israel by birth, or perhaps even by baptism, that that connection will assure them salvation. That is what is meant when the sons of Jacob ask, “Wherein shall we return?” In other words, how can we return if we are already part of the covenant?
Jehovah declares that even those under the covenant can rob God of his just dues, and the obedience required as the human part of the covenant. Again, the sons of Jacob might wonder if it was possible that they had robbed God.
Jehovah answers that the whole nation had robbed him, and therefore is under condemnation. The specifics come in the next verses.