By being a Christian, one has pledged to carry on Christ’s love.
To love as Jesus does is to do extra, to go "more than a mile" (Mt. 5:41), to go beyond our ordinary human transactions. To love those whom you know as friends is not "extra." To give to those who have given you in return in not "more." To work because you are paid a salary is not "beyond." To give in order to be given in return is the form of honor, praise, promotion is not "extra."
All these--friendship, salary, honor, praise, promotion are ordinary human ground of transaction; everybody, even pagans related himself within this familiar ground.
Christ challenged us to go across the familiar ground and explore the unfamiliar, unknown:
To love those who are not lovable is "extra."
To give to those who cannot give in return is "more."
To serve those who cannot serve in return is "beyond."
To forgive even your enemy is "extra."
To explore the unfamiliar ground with Christ's love is going more than a mile. Only the extra-miler deserves the name "Christian."