" We can only claim from him justice- and justice, for us, means certain condemnation. God does not owe it to anyone to stop justice taking its course. He is not obliged to pity and pardon; if He does so it is an act done, as we say 'of His own free will,' and nobody forces His hand. 'It does not depend on man's will or effort, but on God's mercy'(Rom. 9:16 NEB). Grace is free, in the sense of being self-originated and of proceeding from One who was free not to be gracious. Only when it is seen that what decides each individual's destiny is whether or not God resolves to save him from his sins, and that is a decision which God need not make in any single case, can one begin to grasp the biblical view of grace."
J.I. Packer - Knowing God