Why does God test people if he already knows what they'll do?

The clearest biblical example is God testing Abraham by asking him to sacrifice his son Isaac. Afterward, God says, "Now I know that you fear God"—language that raises exactly this question, since God presumably already knew Abraham's heart.

Most interpreters read the purpose of testing as being for the person's own benefit and for others watching, not for God's information. The test reveals, publicly and to Abraham himself, a faith and character that was real but not yet demonstrated in action—similar to how a difficult exam doesn't teach a teacher something new about a subject, but does reveal and confirm what a student genuinely knows.

Deuteronomy makes a similar point about Israel's wilderness testing: it was meant "to know what was in your heart"—read by most Christians as revealing character through action, both to the person and to others, rather than informing an otherwise uncertain God.