but if you refuse and rebel, you shall be eaten by the sword; for the mouth of the LORD has spoken.”
20. But if ye refuse and rebel The wicked always think that the severity of the punishment is greater than their guilt, even though the Lord chastise them very gently; and although they do not venture to justify themselves entirely, yet they never cease, as I formerly said, to accuse God of excessive severity.
Though God had rejected their services as insufficient to atone for their sins while they persisted in them, yet he does not reject them as in a hopeless condition, but here calls upon them to forsake their sins, which hindered the acceptance of their services, and then all would be well. Let them not say that God picked quarrels with them; no, he proposes a method of reconciliation.
Commenting on Isaiah 1:16-20
But if ye refuse and rebel,.... The Targum is, "and do not receive my Word"; the Messiah, when come, neither his person, nor his doctrines and ordinances: ye shall be devoured with the sword; of the Roman armies, as they were under Titus Vespasian; see Mat 22:7. for the mouth of the Lord hath spoken it; now, by Isaiah, as well as in former times, Lev 26:25.