Summary: There is tremendous power in our words as God’s children.
The Power and Authority of Words
In the New Testament, the Greek word for "authority" is sometimes translated as "power." Even though there is a separate Greek word for power, the concepts of power and authority are so intimately connected in the Western mind, that modern translators often view them as synonyms. But translations aside, there is a biblical distinction that should be made between authority and power.
If we consider the relationship between author and authority, you will agree that an author has "authority" because he is the originator, the creator. Authority, in the biblical sense, is usually referring to the legitimacy of the individual or individuals. For example, when Jesus finished his Sermon on the Mount, Matthew records that "the crowds were amazed at His teaching; for He was teaching them as one having authority, and not as their scribes" (Matthew 7:28-29). In other words, the crowds recognized something different in the words of Jesus that was lacking in the words of their own teachers. The scribes had the "power" of the Scriptures, but lacked the ability—the legitimacy—to speak them with any authority. When Jesus, the author and finisher of faith (Hebrews 12:2) spoke however, he spoke with authority because he was the author; he had legitimate claim to the power AND authority of the Scriptures.
Words are important to God. He gave us His word—the Bible—and he gave the Word—Jesus Christ. He made words the focus of two of His ten commandments: the third and the ninth. In the third commandment, we are told to not take his name in vain, referring primarily to vows and oaths. In the ninth, we are told to not bear false witness against our neighbour, a reference to being truthful and providing trustworthy testimony. God expects his people to be truthful, to be without reproach in what we say and do. This idea is repeated over and over throughout the entire Bible and when we get to the New Testament we find an interesting application of this concept.
In the Sermon on the Mount, Jesus makes an observation regarding the third commandment. In Matthew 5:33-37, Jesus says: "You have heard that it was said to those of old, ‘You shall not swear falsely, but shall perform your oaths to the Lord.’ But I say to you, do not swear at all: neither by heaven, for it is God’s throne; nor by the earth, for it is His footstool; nor by Jerusalem, for it is the city of the great King. Nor shall you swear by your head, because you cannot make one hair white or black. But let your ‘Yes’ be ‘Yes,’ and your ‘No,’ ‘No.’ For whatever is more than these is from the evil one." Paul and James both repeat similar admonitions in their letters (2 Corinthians 1:17-20; James 5:12).
The Name in Vain
The Third Commandment states: "You shall not take the name of the Lord your God in vain, for the Lord will not leave him unpunished who takes His name in vain" (Exodus 20:7). Although this commandment is typically understood to mean how we use the name of God in our speech, this is not primarily what is being commanded. Notice that the verse says "take" not "use" the name of the Lord in vain. While "using" God’s name improperly is certainly implied, it is not the main point of the Third Commandment.