The prophet speaks of a righteous group of people in the last days, and the Lord will write the law in their hearts. Jeremiah taught this same doctrine when he spoke of the new and everlasting covenant to be revealed in the last days, ’I will make a new covenant with the house of Israel…I will put my law in their inward parts, and write it in their hearts, and will be their God, and they shall be my people.’ (Jer 31:31-33) How will the Lord write the law in their hearts?
The Lord always commands his prophets to write down his laws. In this instance, he is writing the law in the hearts of the righteous. This is exactly what happens when the saints attend the temple—they learn the law of the Lord. However, this law cannot be written down on parchments or stone tablets. Rather, through regular temple attendance and sheer repetition, it is written in the hearts of the temple patrons.