See How Great A Love

John 13:34,35 - The new command is simple enough for a toddler to memorize and appreciate, profound enough that the most mature believers are repeatedly embarrassed at how poorly they comprehend it and put it into practice: Love one another. As I have loved you, so you must love one another. . . The more we recognize the depth of our own sin, the more we recognize the love of the Saviour; the more we appreciate the love of the Saviour, the higher his standard appears; the higher his standard appears, the more we recognize in our selfishness, our innate self-centredness, the depth of our own sin. With a standard like this, no thoughtful believer can ever say this side of the parousia, 'I am perfectly keeping the basic stipulation of the new covenant.'

-- D.A. Carson, The Gospel According to John