“It is God's holiness that makes Him faithful in all His promises. When the doubting man reads the precious promises given to returning sinners, why cannot he take comfort in them? Surely it is because he is still not sure God is faithful enough to perform them.
But the strongest argument which faith has to put this question out of doubt, and cause the sinner to accept the promise as a true word, rests in the holiness of God, the Promise Maker. He gently persuades the person to trust Him by prefixing His promises with the attribute of holiness: "I will help you, says the Lord, and your redeemer, the Holy One of Israel" Isaiah 41:14. The Hebrew word for "mercies" is often translated "holy things," and because God's mercies are founded in His holiness, they are therefore sure mercies, Isaiah 55:3. How many times did Laban change Jacob's wages after his promise? Yet God's covenant with Jacob was always kept, although Jacob was not faithful on his part. Why? Because he was dealing with the holy God.
Another of God's attributes which kindles fear in the awakened sinner is His justice. The soul sees no way except hell for God to vindicate His justice. But faith empowers the soul to walk around in this fiery attribute with His comfort unsinged, even as the Hebrew children prospered in the flaming furnace Daniel 3.
Faith relieves the soul, which fears God's justice. One might wonder whether or not God can be both just and righteous in pardoning a sinner. Faith shows that God may pardon sins, no matter how great, with safety to His justice. This question was settled, at the council board of heaven by God Himself and He has expressed His decision in the form of a precious promise: "I will betroth you unto me forever; yes, I will betroth you unto me in righteousness, and in judgment." Hosea 2:19.”
Quoted material from, ”The Christian in Complete Armour Daily Readings in Spiritual Warfare” by Gurnall and James S Bell. http://www.moodypublishers.com/pub_productDetail.aspx?id=41823&pid=53617