Christians should be recognized and distinguished from the rest of the world by the difference in their practice.
Which practice are we referring to?
My heart is always drawn to the specific teachings of Jesus on the sermon on the mount. That sermon is recorded in three of the four gospels, indicating that each of the gospel writers thought it was important enough of an address to place it in.
Glen Stassen, a professor in Christian Ethics writes this:
The church confesses that Jesus of Nazareth is the Messiah…but here is the problem: Christian churches …are often guilty of evading Jesus, the cornerstone and center of the Christian faith. Specifically, the teachings and practices of Jesus–especially the largest block of his teachings, the Sermon on the Mount…
Jesus taught that the test of our discipleship is whether we act on his teachings…the evasion of the teachings constitutes a crisis of Christian identity and raises the question of who exactly is functioning as the Lord of the church.
Glen Stassen in his book Kingdom Ethics
I think Stassen has an excellent point. In many respects, the Sermon on the Mount form a picture of what a Christian looks and behaves like in the context of their world.
As Christians, the Sermon on the Mount should be a focus and a continually challenge for us in regards to what it looks like to be light and salt in the world.