They will know we are Christians by our love.
Christians do not dress differently from others. We do not speak another language or wear our hair differently. We eat the same foods as everyone else. What marks us as Christians is that we strive to love as Jesus loved. Everything we do - from the simplest act of kindness to the bravest display of heroism - we seek to do with great love in imitation of our Savior, Jesus Christ. Just as importantly, we claim that nothing we do has any value unless it is done with love. Love makes all things pleasing to God. And so, we are meant to stand out from the crowd by our acts of love.
We have many names for God and many ways of describing him. We call him God the Almighty and Lord of Hosts. We call him our Creator. We describe him as just and merciful. In imitation of Jesus, we call him Father. But, the truest description of the God who is revealed in Jesus Christ is that he is love. God loves the world and all the people he created. He loves each of us. It is a marvel beyond the capacity of our minds to grasp and our imaginations to perceive. The One who made everything, the One who holds all creation in his hands, the One who guides all of history knows each of us and loves each of us!
Because God is love, when we love one another we are imitating God. Furthermore, since we are created in God's image and likeness, we are most fully ourselves and most fully alive when we love. Through love, we are fulfilling God's will for us. When we love, we are keeping all of God's commandments.
When Jesus is asked in the gospel to single out the greatest commandment of the Law, he replies with a quote from the book of Deuteronomy: "You shall love the Lord your God with your whole heart, with your whole soul and with all your mind". There is nothing new in this commandment. In fact, pious Jews recite it every day in their prayers. What Jesus does do which is new is that he connects this commandment with another commandment from the book of Leviticus, "You shall love your neighbor as yourself." Now, loving God and loving neighbor go hand in hand. We cannot claim to love God and, all the while, despise our neighbor. This theme is repeated in today's first reading from the book of Exodus. God tells the people that if they abuse the foreigner and the poor, he will surely hear their cry. Because God loves and protects them, he expects us to love and protect them as well. In Jesus, there is no separating the worship we bring to the Father from the love we show our brothers and sisters.
Jesus did something else which is totally new. Not only did he teach us that love of God and love of neighbor go hand in hand, but he gave us the greatest example of love, an example of love which we are to follow. He gave his life to save us. As he told his disciples at the Last Supper, "There is no greater love than to give one's life for a friend." The love that Jesus teaches us to live is no warm feeling. It is a love which requires us to sacrifice ourselves for others. It is a love which compels us to act. It is the love of Saint Peter Claver who brought comfort to and fought for the release of slaves in the Americas. It is the love of Blessed Damien of Molokai who risked his health to serve lepers in Hawaii. It is the love of Saint Francis of Assisi who left all his possessions behind and the wealth of his father's house to be among the poor. It is the love of Mother Theresa who looked after the dying in the gutters of Calcutta. It is the love of Saint Maximilian Kolbe who, in a Nazi concentration camp, took the place of another man who was sentenced to death. We might not all be called upon to display such heroism. Most of us will show love in less dramatic and less costly ways. Nonetheless, when we love as Jesus loved we will be like him and bring his presence to those we meet.
Mother Angelica in her Little Book of Life Lessons & Everyday Spirituality, puts it this way:
We have the wrong idea of Christianity. We don’t understand that to know Jesus is to want to be like Him. Do you notice that after people reach fifty years of married life they put their pictures in the paper, and they look alike? Love does this. Love makes you like the person you love. If you really loved Jesus, you would look more and more like Him, each day. It isn’t who you are or what you are or how good or bad you are, you have been commissioned by God to reflect one of His attributes. Some of you will reflect the mercy of God by forgiving. Some of you will reflect the silence of God. Some will reflect the sweetness of God. You are to bear fruit for the glory of the Father. By conforming yourselves to God’s Will, you reflect, in a very small way, some of the beauty of God.
Now, imagine what the world would be like if we were all like Jesus. What if we all loved one another and puts the needs of others before our own needs. Imagine if no one went to sleep at night until they were sure that everyone else had something to eat and a warm place to sleep. This is not just an exercise in wishful thinking. It is the commandment of Christ. It is what Jesus expects of us who would call ourselves Christians - that we love one another as he has loved us.