Unbelief grieves the heart of God more than any other sin. We Christians cry out against the sins of the flesh but God is concerned with the sins of the heart — doubting his Word or questioning his faithfulness. The real issues of life and death have more to do with how a person thinks than what he does.
I have known Christians who forsake every sin of the flesh they can think of but in spite of “cleaning up their act,” they are still restless and dissatisfied. They mistakenly thought God would be pleased if they forsook their secret sin, that the blessings would flow automatically. But sins of the flesh are only part of the problem. They learned only to fear the Lord but not to trust him, and fear almost always gives birth to unbelief.
Through his Word God has graciously provided a sure way to have absolute confidence in him.
“When you lie down, you will not be afraid; yes, you will lie down and your sleep will be sweet. Do not be afraid of sudden terror, nor of trouble from the wicked when it comes; for the Lord will be your confidence, and will keep your foot from being caught” (Proverbs 3:24-26).
“Therefore do not cast away your confidence, which has great reward” (Hebrews 10:35).
“Now this is the confidence that we have in Him, that if we ask anything according to His will, He hears us. And if we know that He hears us, whatever we ask, we know that we have the petitions that we have asked of Him” (1 John 5:14-15).
These are marvelous promises from our heavenly Father. Do not give in to fear or doubt! Deal with unbelief as you would any other abominable sin. Fix your heart to trust in the Lord — and remember the words of the Psalmist: “He will not be afraid of evil tidings; his heart is steadfast, trusting in the Lord. His heart is established; he will not be afraid” (Psalm 112:7-8).