Most people reply, "John 3:16."
Have you ever pondered the riches contained in this single verse?
Over at ScriptoriumDaily, Fred Sanders does just that. First, he considers its proper translation:
The verse doesn’t say “God loves the world so much that he sent his Son,” rather it says “Look at this, this right here is the way God loved the world: he sent his Son.” God loved like this! As a pointer-word, “so” directs your attention like an index finger toward a thing so unparalleled and singular that all we can do it look and learn. And it points to a past action, an event already accomplished. Think how much we lose when we unconsciously dumb this verse down to “How much God loves the world” (present tense, emphasizing magnitude) rather than what it wants to show us: Here is how God loved the world!Then, Sanders outlines what John 3:16 says about the doctrine of revelation, Scripture, God, Christ, sin, and salvation.
It's a brief and interesting article. Have a look.