Nope. I think it’s love.
What does the greatest command hinge upon? Love. What will be the defining characteristic of followers of Jesus? Love. What will never pass away, even after faith and hope are gone? Love.
Love is the mark of the disciple. But here’s the problem: You can’t teach love.
You can teach how to effectively memorize Scripture, everything from acrostic memory devices to methods of placing cards for reading at strategic places. Similarly, you can teach someone how to fast – what to expect on day 1, 2, and so forth, and how to respond to the temptation of hunger. You can teach someone how to pray. The tools abound in terms of journals, philosophies, and books. But how do you teach someone to love?
This is perhaps the one element of discipleship that can’t be faked. Surely there are many, according to Jesus, who might perform miracles, drive out demons, and do all other kinds of religious things that will not enter the kingdom of heaven. We can become very adept at “playing disciple” by our sheer acts of will. We can even force ourselves into positions of service and postures of generosity. But love? Real genuine love? That’s something you can’t manufacture.
Nevertheless, Jesus said that “By this everyone will know that you are my disciples, if you love one another” (John 13:35). Despite this statement, all our current metrics of discipleship focus on things like knowledge of the Bible and time spent in prayer. Those are all also important marks of discipleship, but love is infinitely more difficult (and perhaps impossible) to quantify.
Nobody ever loved by gritting their teeth and deciding to do it. It’s not like that. True, love is grown over time, and like most other things, our appetite for love grows through exercises of the will. That is, we choose to engage in activities of love even when we don’t feel like it because we believe that in doing so, our love will grow. But ultimately, even these actions can’t force us to love.
That’s actually why, I think, love is the defining characteristic of discipleship – because love – true love – can only come from a true, vibrant, and constant experience of the gospel. The gospel is what love is – that’s the true measure of love. Those who truly love demonstrate they have been loved and are growing in their understanding of the great love of God in Christ.