Most of us have been in the situation where someone's name has slipped our memory, though we can, we believe, "still see his/her face as clear as yesterday". Sometimes we can have an interesting "wrong number" telephone conversation, but there is something missing if it remains anonymous.
Of course, some people know all the right names, but don't really know the people concerned. They are just "name-droppers" - using other people's names to boost their self-image.
In the third commandment, the Lord says to us, "Do not use my name for evil purposes, for I, the Lord your God, will punish anyone who misuses my name." (Ex. 20.7)
The LORD had called his people into a personal relationship with himself (note v. 2). This relationship must be expressed in their worship and in their lives - whatever name-word for God they might end up using.
Of course, it was clear that the Name must not be used in false testimony - nor in magic incantations. But the reference was (and is) much broader than this.
The command certainly excludes the profane or careless use of God's name (so common today) - it is a very serious matter to use God's name and "mean nothing by it". Also excluded is hypocrisy, so strongly condemned by Jesus - the taking of the Name on oneself to claim a relationship with God which is not real. It also excludes the presumptuous use of the name - the claim to do things in the name of God without his authority and blessing.
The command gives a solemn warning - "I, the Lord your God, will punish anyone who misuses my name". Sometimes we may be inclined to take this command as if it is a fairly mechanical matter of not very great consequence. But it is centrally concerned with a living, vital relationship with the Lord. The breakdown of this relationship is very serious.
We need the corrective of the negative command, but have not kept it fully until we are led to positive obedience. The warning against the wrong use of the Name should not lead us to the non-use of the Name but to the right use of it - in sincere prayer and in consistent Christian living.
Jesus makes this clear in his solemn words near the end of the Sermon on the Mount - "Not everyone who calls me 'Lord, Lord' will enter the Kingdom of heaven, but only those who do what my Father in heaven wants them to do. When Judgement Day comes, many will say to me, 'Lord, Lord! In your name we spoke God's message, by your name we drove out many demons and performed many miracles!' Then I will say to them, 'I never knew you. Get away from me, you wicked people!' " (Mt. 7.21-23).
The well-known parable of the wise man and the foolish man follows. This emphasises the importance of not only hearing the words of Jesus but doing them. The words "not every one", while a warning against using his name in vain, also clearly imply the necessity of calling him Lord.
Peter makes clear that this "calling on the name of the Lord" involves both repentance (acknowledgment of sin and turning from it) and faith (trust or dependence on the forgiveness of sins made possible in Jesus Christ).
It is quite clear that, from the earliest Christian times, the divinity of Jesus Christ had been recognised (note other references to this verse in Rom. 10.13 and 1 Cor. 1.2). We note what Peter said about Jesus to the Jewish leaders - "Salvation is to be found through him alone; in all the world there is no one else (literally, no other name) whom God has given who can save us" (Acts 4.12).
We must, then, call on his name and this involves genuine repentance and faith.
This claiming of the Lord's name was not always genuine. Yet where it is genuine it speaks of the new relationship with God which belongs to those who have come to Him in repentance and faith. They are born anew (Jn. 3) and as true children of God can approach him as Father (note the Lord's Prayer).
We are to pray "in Jesus' name" - coming as God's children and as Christ's servants.
In other words, "Lord" must be always be more than a name-word for God - it must express a relationship and a whole attitude of life. Anything less is to take the Lord's name in vain.