Romans 4:8 Blessed is the man to whom the Lord will not impute sin.
It is not that He cannot, it is that He will not. Exactly what is it that the Lord denies doing and why? The object is sin and the verb is impute. While looking up the Old Testament definition of impute I found the earliest use was in Genesis 2:8 when God put the man in the garden. It is also used in conjunction with putting a man in prison.
The boarder meaning is used to plants ones seed, as in to father a child. It is also used in context to plant fruit bearing trees. So how does this relate to Romans 4:8?
Romans 6:5 For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection:
One can only grow what has been planted.
Ephesians 3:17 That Christ may dwell in your hearts by faith; that ye, being rooted and grounded in love,
2 Corinthians 9:10 Now he that ministereth seed to the sower both minister bread for your food, and multiply your seed sown, and increase the fruits of your righteousness;
Philippians 1:11 Being filled with the fruits of righteousness, which are by Jesus Christ, unto the glory and praise of God.
Psalm 1:3 And he shall be like a tree planted by the rivers of water, that bringeth forth his fruit in his season; his leaf also shall not wither; and whatsoever he doeth shall prosper.
Matthew 7:19-20 Every tree that bringeth not forth good fruit is hewn down, and cast into the fire. Wherefore by their fruits ye shall know them.
Romans 5:13 For until the law sin was in the world: but sin is not imputed when there is no law.
You are imputed grace not law, so sin is cannot take root.