God's Law in the Heart

For this is the covenant that I will make with the house of Israel after those days, saith the Lord; I will put my laws into their mind, and write them in their hearts: and I will be to them a God, and they shall be to me a people. Hebrews 8:10. 
 
The blessings of the new covenant are grounded purely on mercy in forgiving unrighteousness and sins. The Lord specifies, I will do thus and thus unto all who turn to Me, forsaking the evil and choosing the good. “I will be merciful to their unrighteousness, and their sins and their iniquities will I remember no more.” (Hebrews 8:12). All who humble their hearts, confessing their sins, will find mercy and grace and assurance. 
 
Has God, in showing mercy to the sinner, ceased to be just? Has He dishonored His holy law, and will He henceforth pass over the violation of it? God is true. He changes not. The conditions of salvation are ever the same. Life, eternal life, is for all who will obey God’s law. Perfect obedience, revealed in thought, word, and deed, is as essential now as when the lawyer asked Christ, “What shall I do to inherit eternal life?” Jesus said to him, “What is written in the law? How readest thou? .... This do, and thou shalt live” (Luke 10:25-28). 
 
Under the new covenant the conditions by which eternal life may be gained are the same as under the old—perfect obedience. Under the old covenant there were many offences of a daring, presumptuous character for which there was no atonement specified by law. In the new and better covenant Christ has fulfilled the law for the transgressors of law if they receive Him by faith as a personal Saviour.... Mercy and forgiveness are the reward of all who come to Christ trusting in His merits to take away their sins. In the better covenant we are cleansed from sin by the blood of Christ.... The sinner is helpless to atone for one sin. The power is in Christ’s free gift, a promise appreciated by those only who are sensible of their sins and who forsake their sins and cast their helpless souls upon Christ, the sin-pardoning Saviour. He will put into their hearts His perfect law, which is “holy, and just, and good” (Romans 7:12), the law of God’s own nature.