Faithful and Just
The verse 1 John 1:9 is familiar to us:
If we confess our sins, [God] is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.
Calvin vividly describes what it would be to live without this blessing of forgiveness:
It is of great moment to be fully persuaded, that when we have sinned, there is a reconciliation with God ready and prepared for us: we shall otherwise carry always a hell within us. Few, indeed, consider how miserable and wretched is a doubting conscience; but the truth is, that hell reigns where there is no peace with God. The more, then, it becomes us to receive with the whole heart this promise which offers free pardon to all who confess their sins. — Commentaries on the Catholic Epistles
Calvin goes on to comment on the fact that God’s justice or righteousness is spoken of here, where we might expect to see his mercy mentioned instead:
Moreover, this is founded even on the justice of God, because God who promises is true and just. For they who think that he is called just, because he justifies us freely, reason, as I think, with too much refinement, because justice or righteousness here depends on fidelity, and both are annexed to the promise. For God might have been just, were he to deal with us with all the rigor of justice; but as he has bound himself to us by his word, he would not have himself deemed just, except he forgives.