Isaiah 63

As Isaiah writes of the second coming of the Savior, he asks the question -

"Wherefore art thou red in thine apparel, and thy garments like him that treadeth in the winefat?"  (Old Testament | Isaiah 63:2)

The Lord answers  -

"I have trodden the winepress alone; and of the people there was none with me: for I will tread them in mine anger, and trample them in my fury; and their blood shall be sprinkled upon my garments, and I will stain all my raiment."  (Old Testament | Isaiah 63:3)

As much as we picture the Savior being a God of mercy, at the same time, it is clear that He is a God of justice for Alma taught his son-

"...do ye suppose that mercy can rob justice? I say unto you, Nay; not one whit. If so, God would cease to be God."  (Book of Mormon | Alma 42:25)

The conditions of the law are such that if we repent and keep His commandments we may obtain mercy for -

"I will mention the lovingkindnesses of the LORD, and the praises of the LORD, according to all that the LORD hath bestowed on us, and the great goodness toward the house of Israel, which he hath bestowed on them according to his mercies, and according to the multitude of his lovingkindnesses.
8 For he said, Surely they are my people, children that will not lie: so he was their Saviour."  (Old Testament | Isaiah 63:7 - 8)

They "that will not lie", in my mind, are they that keep the covenants they have made with the Lord.