Charles Spurgeon Commentary Romans 7:4

"Wherefore, my brethren, ye also were made dead to the law through the body of Christ; that ye should be joined to another, [even] to him who was raised from the dead, that we might bring forth fruit unto God." — Romans 7:4 (ASV)

While we were under the law, we could not come under the new covenant—the covenant of grace. But, through the death of Christ, we are dead to the law, and therefore we are set free from the principle and covenant of law, and we have come under the covenant of grace.