“… Jesus Christ… was… declared to be the Son of God… according to the spirit of holiness, by the resurrection from the dead” (Rom. 1:3,4).
What does it mean that the Lord’s resurrection declared Him to be the Son of God according to the spirit of holiness? Well, have you ever heard it said that there is a difference between the letter of the law and the spirit of the law? When you drive 66 m.p.h. in a 65 m.p.h. zone, you are breaking the letter of the law, but you are not breaking the spirit of the law. The spirit of the law is for you to drive safely and responsibly. This is why most police officers will not ticket you for going one mile per hour over the speed limit.
The letter of the law of holiness is expressed well in Proverbs 17:15:
“He that justifieth the wicked, and he that condemneth the just, even they both are abomination to the Lord.”
But isn’t that what God did at the Cross, when He condemned “that Just One” (Acts 22:14) and justified wicked sinners such as ourselves? In so doing, He surely broke the letter of the law of holiness.
Or did He? For those who would argue that God was not acting in accord with the law of holiness, we would reply that when God the Father took your sins and placed them on the Lord Jesus Christ at Calvary, He justly condemned the One who was made wicked (II Cor. 5:21). Then when you believed the gospel, God took His righteousness and put it on you, enabling Him to justify the ones who were made the very righteousness of God in Christ (II Cor. 5:21). The resurrection of Christ then proved that this was also done in perfect accord with the spirit of holiness, for Christ’s sacrifice surely satisfied the just demands of God’s righteousness.
If you haven’t yet trusted Christ as your Savior, however, God has not yet given you the righteousness that is available only in Christ. Speaking of the Lord Jesus, the Apostle Paul says,
“In whom we have redemption through His blood, the forgiveness of sins, according to the riches of His grace” (Eph. 1:7).
The forgiveness of sins purchased by Christ’s blood is only available in Him. If you are not in Christ, you are still “in trespasses and sins” (Eph. 2:1). “Believe on the Lord Jesus Christ, and thou shalt be saved” (Acts 16:31). source