To say that someone is ‘LORD’, is to admit that they are the one in charge. Jesus continually demonstrated His Lordship and sovereignty over all things, thus proving, continually, that He was the one in control of everything. He was the Lord of nature who with a single word calmed a storm. He was the Lord over death who by His word raised the dead. He was Lord over Satan who by a word cast out demons. This kind of sovereignty is God’s domain! Is it any wonder then that Jesus gave an uninterrupted demonstration that He was the Lord?
The Greek word for Lord is ‘Kurios’: it means ‘Supreme Authority’. This is the word that was continually used to translate the Tetragrammaton (a four-letter Hebrew name) which stood for the name of Yahweh in the Greek translation of the Old Testament (the Septuagint). The early Christians, knowing the usage of this word Kurios, refused, therefore, to swear an oath of allegiance to the Roman Emperor. And what was the oath? They were required to declare, “Cesar is the Kurios” which meant, “Caesar is the Lord.” Along with the oath they were also required to burn incense to the Emperor’s image. The Roman state saw this as an affirmation of political loyalty, but the Christians saw it quite differently. They saw this as an idolatrous act that betrayed Christ. In their enlightened understanding, there was only one Kurios—Jesus! There could be only one supreme authority. Since there is no authority higher than that which is supreme, the Christians knew that to declare the Emperor the Kurios would be to declare him to be God. They, therefore, refused to do so and paid for their actions with their lives.
There are those who point out that the term ‘kurios’ could have been used of anyone in a position of authority. It could, in fact, refer to anyone who was a leader, a property owner, a head of household, a slave owner, and even a husband could be called “Lord”. This is true, but when the apostles used the term Lord they were declaring Jesus to be much more than a leader, property owner or head of a household; they were declaring Him to be God. The early Christians weren’t killed for refusing to declare Caesar as being the head of his household, they were killed for refusing to call the Emperor God. Jesus was their God, there was room for no other.
The apostles urged their listeners to call upon the name of the Lord, the mighty God, the sovereign, supreme authority. In Romans 10:9, Paul declared:
“if you confess with your mouth the Lord Jesus... you shall be saved.”
Then in Romans 10:13, Paul backs up this declaration by quoting from the Old Testament:
“For whoever will call upon the name of the LORD shall be delivered (saved)” (Joel 2:32).
It is remarkable to note that when Joel 2:32 is quoted in both Acts 2:21 and Romans 10:13, the “LORD" in question is identified as Jesus. This is all the more significant when we remember that the Jewish faith had always insisted that the people should call upon the name of Yahweh (“Psalm 17:6; Psalm 116:4; Lamentations 3:55).
But when we reach the pages of the New Testament, we see Jewish Christians insisting that people should no longer call on Yahweh, the Old Testament name of God, but now they must call only on the name of Jesus: Their conviction concerning Jesus was, "there is no other name under heaven given to men by which we must be saved” Acts 4:12.
The early Christians were persuaded that to call Jesus Lord was to call him Yahweh. This being so, we should inform the cults that, in reality, they cannot make the confession, “Jesus is Lord” because these three words are a confession of Christ’s supreme deity!
And that’s the Gospel Truth!