Read 1 Samuel 17.

Goliath was a huge man. He stood about 9 1/2 feet (2.9 metres). Even from a distance he intimidated the Israelites and as they looked at him they wondered how they would ever win the battle against the Philistines. 

In those days, battles were sometimes decided between champion fighters for each army. Rather than a huge bloody war, one person from each nation was selected to fight and through them the nations fought against each other (and one god against the other). This was Goliath's challenge day after day after day. And each day the Israelite army saw this giant step forward with his shield bearer and heard him utter his challenge, but no one dared to fight. Why bother? How do you kill a giant? Have you seen the size of his spear? In verse 11 it says, "On hearing the Philistines words, Saul and all the Israelites were dismayed and terrified."

But along comes David, who hears these curses being lobbed at Israel and sees the army quaking in fear. He knows how ridiculous it is. He says to Saul, "Let no one lose heart on account of this Philistine; your servant will go and fight him." (verse 32)

By no means was David equal in size, stature, or intimidation to Goliath, but he knew something the rest of the army seemed to forget. God was with them, and God would be with him.

David said to Goliath, after being insulted for his size, "You come against me with sword and spear and javelin, but I come against you in the name of the Lord Almighty, the God of the armies of Israel, whom you have defied. ... All those gathered here will know that it is not by sword or spear that the Lord saves; for the battle is the Lord's, and He will give all of you into our hands." (verses 45, 47)

That's just what God did. With the flick of his sling shot David struck down Goliath and defeated the Philistines.

Now ... this doesn't mean that God will give us victory over whatever giant stands in our way like God did for David if we just believe enough. What this story of David and Goliath shows us is that all-to-often we think that battle is our own. We stand with the Israelites and look at the things against us and think, "Wow! That's a big problem!" or, "I am powerless to change that," or "I'm not big/strong/smart/creative enough," and we do nothing but stare at our problems and lose hope and act defeated.

What can I do? I'm just one person, I'm just me.

But, as David shows us: our hope doesn't come from within us. David didn't have that courage to go into battle because he was so strong. He went because he knew God was with him. And we know that too: God is with us. That's the whole story of Christmas -- Emmanuel, God with us.

And that's why we have hope today. God is with us. 

(Also, the kind of battle David and Goliath fought is a great way for us to see what Jesus did for us on the cross. In the battle against sin and death, Jesus stood in our place as our champion. Our fate was tied up in Him. He fought for us. He died for us. But his death wasn't defeat, it was victory, because when he was raised from the dead on the third day His victory over sin and death was/is our victory. As our champion, He accomplished for us what we could never do. And so, through Him, we always have hope.)