Out of the Horse's Mouth - 1 John 1:1 - 4

We know Scripture is the Word of God, breathed out by the Holy Spirit as He guided the biblical authors as they were writing. But do we ever think about the fact that the biblical authors knew first hand that what they were writing was absolute Truth? The Bible is completely trustworthy because if is the Word of God, but isn't is comforting that God used those who knew Him personally to write it down? His Word comes to us right out of the Horses' mouth!