Immediately the father of the child cried out
and said, “I believe; help my unbelief!”
–Mark 9:24 (ESV)–

Take care, brothers, lest there be in any of you an evil, unbelieving heart,
leading you to fall away from the living God.
–Hebrews 3:12 (ESV)–

The wrath of God is being revealed from Heaven
against all the godlessness and wickedness of people,
who suppress the truth by their wickedness.
–Romans 1:18 (NIV)–

Without faith it is impossible to please God,
because anyone who comes to him must believe that he exists
and that he rewards those who earnestly seek him.
–Hebrews 11:6 (NIV)–

—

Josh McDowell, More Than a Carpenter.

Ken Ham, “Young Earth Creationism,” Creation, Evolution, and Intelligent Design.

Norman Geisler, When Critics Ask.

—. When Skeptics Ask.

J. Gresham Machen, Christianity and Liberalism.

Roger Olson, Against Liberal Theology.

Charles Spurgeon, 12 Sermons on Unbelief.