4. The means by which they shall be kept tight and faithful to the covenant on their part: Thou shalt know the Lord. This is not only a promise that God will reveal himself to them more fully and clearly than ever, but that he will give them a heart to know him; they shall know more of him, and shall know him in another manner than ever yet. The ground of their apostasy was their not knowing God to be their benefactor (v. 8); therefore, to prevent the like, they shall all be taught of God to know him. Note, God keeps up his interest in men's souls by giving them a good understanding and a right knowledge of things, Heb. viii. 11.