Although the early Christians were a minority in the Roman Empire and often persecuted, they took pains to obey the laws of the land. That is what we learn from the writings of second-century Christians such as Justin Martyr, who was one of the first apologists (defenders of the faith). These early Christians paid their taxes, prayed for the emperor, and fulfilled their civic duties. There was one demand placed upon them, however, that they could not meet. When the authorities ordered them to say, “Caesar is Lord,” they refused. There was only one whom they would acknowledge as “Lord,” namely, the Lord Jesus Christ.
When we understand the meaning of the word Lord in Scripture as well as the claims of the Roman emperors, we will see why the early Christians referred to Jesus alone as Lord. “Lord” is the English translation of the Greek word kurios, which is typically used in the Septuagint, the ancient Greek translation of the Old Testament, to translate the Hebrew tetragrammaton—the covenant name of the God of Israel. That is, when the ancient Greek translators translated God’s name Yahweh, they typically did so using the Greek word kurios.
If kurios is used for the divine covenant name, then for the Jews to apply that title regularly to someone at least implies that they viewed the person who held the title as deity. Now, we must note that kurios in Scripture can be used of ordinary people, but its use for the divine name is striking, particularly when it is so frequently given to Jesus in the New Testament. The earliest Christians such as Peter and Paul were all Jews, yet they had no difficulty calling Jesus kurios, that is, “Lord” (Phil. 2:5–11; 1 Peter 1:3). In fact, the word kurios appears hundreds of times in the New Testament, and it is usually used for Jesus. This is an awfully strange phenomenon if the Apostles did not believe Jesus was God incarnate, for they could have used other titles for Him. The Apostles called Jesus “Lord” because they affirmed His deity (John 20:24–29).
The early church refused to use kurios for the Roman caesars because they were monotheists and would have no other God but the triune God of the Bible. Rome’s emperors often claimed to be deities, so for them to call for their subjects to call them “Lord” was for them to call for their subjects to worship them. The early Christians, rightly, could worship only the true kurios—Jesus Christ, the incarnation of the second person of the Trinity, Yahweh Himself in the flesh.