I heard this idea in a sermon recently, and it's so cool I just had to share it:
Before David could defeat Goliath, he had to go through the valley.
Why did he have to go through the valley?
Because in the valley there was a stream, and in the stream were the five smooth stones he would carry with him to use in his sling.
Here's the key point--
**FROM THE DAY THE WORLD WAS CREATED, GOD HAD BEEN PREPARING THOSE FIVE STONES TO BE THERE, READY FOR DAVID TO USE ON THAT DAY!**
God knew what David would face, and when, and had gone ahead of David to set up everything he would need to be victorious! He led David through the valley to equip him for victory.
'He calls His own sheep by name and leads them out. When He has brought out all His own, HE GOES ON AHEAD OF THEM, and His sheep follow Him because they know His voice.' John 10:3b-4 NIV (emphasis mine)