Jesus didn’t actually say anything about being a Christian. The word ‘Christian’ didn’t come into use until a long time after he left the earth. But a Christian is someone who follows Jesus; and Jesus had a lot to say about what it means to follow him. Most importantly he kept emphasizing that if we want to follow him we must do so wholeheartedly and not allow ourselves to be concerned about other people or things.
There are many stories in the Gospels about people who were distracted from following Jesus by people or things in their lives that they felt were more important. One man was unhappy because Jesus told him to give up his wealth (Luke 18:18-23), others were concerned about family members (Luke 9:59-62).
At the end of John’s gospel Jesus is recorded as making a very important point about following him. He is talking to Peter and says “follow me” (John 21:19). Peter immediately points at one of the other disciples and says “What about him?” Jesus responds by saying that it is not Peter’s concern to wonder about the other disciple and he repeats and reinforces his command. He says “What is that to you? You, follow me.” We are not to look at our brothers and sisters and wonder about them. It is not for us to compare ourselves with them, either favourably or unfavourably. We are called to be servants and Jesus alone is our example. We are called to follow him.
A Christian is someone who follows Jesus and Jesus commands us to follow him wholeheartedly without being distracted by anyone or anything else. This doesn't sound easy; but the more I focus on Jesus’ teachings, reflect on them and pray that I will understand and obey them, the simpler it becomes.