Isaiah 40:8, The grass withers, the flower fades, but the Word of our God will stand forever.
Isaiah is not talking of mere grass here. Just before this, he said, “All flesh is grass” (v. 6). We are the grass and the flower in the metaphor. As all grass withers and all flowers fade, so we wither and fade. The only thing that stands forever is God and His Word.
Is this Law or Gospel? Well, it depends whether you are in Christ or not.
Jesus said, “I am the true vine, and My Father is the vinedresser… If anyone does not abide in Me, he is thrown away like a branch and withers; and the branches are gathered together, thrown into the fire, and burned” (John 15:1, 6).
If you are not in Christ, these words in Isaiah and John are Law—you will wither and burn. If you are in Christ, these words are Gospel—you shall not wither and burn but will, like God’s Word, stand forever. For “you have been born again, not of perishable seed but of imperishable, through the living and abiding Word of God; for ‘All flesh is like grass and all its glory like the flower of grass. The grass withers and the flower falls, but the Word of the Lord remains forever.’ And this Word is the good news that was preached to you” (1 Peter 1:23-25).
Through the imperishable seed of the woman (Genesis 3:15), Jesus Christ the Word incarnate, we become imperishable.
The Lutheran Column 