John Calvin Commentary Isaiah 11:9

"They shall not hurt nor destroy in all my holy mountain; for the earth shall be full of the knowledge of Jehovah, as the waters cover the sea." — Isaiah 11:9 (ASV)

They shall not hurt. He now declares plainly that men themselves, having laid aside the depravity that naturally dwells in them, will be inclined, of their own accord, to do what is right. He speaks of believers who have been truly regenerated to a new life (Romans 6:4), for though many hypocrites full of wickedness were mixed with the elect of God in the Church, they are like the Ishmaelites, whom God will cast out at the proper time.

We ought also to observe, as we are taught in Psalm 15:1 and Psalm 24:3, that only those who follow righteousness have a settled residence in the temple of God, that they may dwell there forever. Therefore, it is a distinguishing mark of the genuine members of the Church that they are free from all desire of doing injury to others. From this, we also infer that it is a remarkable gift of the Spirit of Christ that men abstain from being evildoers, for by nature, ambition, pride, cruelty, and avarice always prompt them freely and voluntarily to commit acts of injustice.

For the earth shall be filled with the knowledge of the Lord. The Prophet adds with good reason that this invaluable blessing flows from the knowledge of God, for it abases all flesh, teaches men to commit themselves to His trust and guardianship, and brings them into a state of brotherly harmony when they learn that they have the same Father (Malachi 2:10).

Although many who have not yet been renewed by the Spirit of Christ profess to have humanity, it is certain that self-love (φιλαυτίαν) reigns in them. For this self-love is natural and so deeply rooted in all people that they seek their own advantage and not that of others; they think that they are born for themselves and not for others and would wish to make the whole world subject to them if they could, as Plato has judiciously observed.

From this arise fraud, perjury, theft, robbery, and innumerable crimes of this sort; therefore, there is no other remedy for subduing this lawless desire than the knowledge of God. We see how the Prophet again makes the government of Christ rest on faith and the doctrine of the gospel. Indeed, Christ gathers us to Himself (Ephesians 1:10) in no other way than by enlightening our minds to reveal the heavenly life, which, as He Himself declares, is nothing other than to know the only true God, and Jesus Christ, whom He has sent (John 17:3).

As with waters that cover the sea. There is an implied comparison between this abundance of knowledge and that slender taste which God gave to the ancient people under the Law. The Jews having been kept in the rudiments of childhood (Galatians 3:23 and Galatians 4:3), the perfect light of wisdom has fully shone on us through the gospel, as was also foretold by Jeremiah: They shall not everyone teach his neighbor, and a man his brother, to know God; for all shall know Me, from the least to the greatest (Jeremiah 31:34).

If this fullness of knowledge takes possession of our minds, it will free us from all malice.

This passage also instructs us about the character of the Church under Popery, where the light of doctrine is choked and almost extinguished, and the highest religion is made to consist in the benumbing influence of brutish stupidity. If we do not immediately possess full knowledge, we must advance from day to day and make continual progress (2 Peter 3:18), and do so in such a manner that fruit may spring from that root. From this it is evident how little progress the greater part have made in the school of Christ, seeing that fraud, robbery, and acts of violence abound everywhere.