God could justly strike all unbelievers down at any moment. Indeed, every breathe we take is proof of His mercy and grace.
And the mistake people make is to think that God's mercy and grace - His silence - means He doesn't care, and that He's not going to do anything about sin. Nothing could be further from the truth. He cares! But He is merciful, and gracious, and patient, and giving people time to repent. But the day will come when His patience will end and justice will be delivered.
Tomorrow's Bible In a Year Passage: Song of Solomon 5:1-8:14, 2 Corinthians 9:1-15, Psalm 51:1-19, Proverbs 22:24-25