Christian formation, according to McKnight, is about relationship with God and with others. Being spiritually mature, then, is about loving well. 

To help us understand this, McKnight describes what he calls the ‘Jesus Creed.' He notes that when an expert in the law of Moses asked Jesus for the greatest commandment, Jesus responded with the Shema, the ancient Jewish creed that commands Israel to love God with heart, soul, mind, and strength. But the next part of Jesus' answer would change the course of history. Jesus amended the Shema, giving his followers a new creed for life: to love God with heart, soul, mind, and strength, but also to love others as themselves.

• “Of all the commandments, which is the most important?” he asked him. “The most important one,” answered Jesus, “is this: ‘Hear, O Israel: The Lord our God, the Lord is one. Love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength.’ The second is this: ‘Love your neighbour as yourself.’ There is no commandment greater than these.” (Mark 12, 28-31)
  

McKnight offers some practical advice on becoming people of this Creed. He writes about particular ways of praying (the Lord’s Prayer and liturgy), approaching God as Abba, learning what he really wants, as well as learning to think of others' needs. 

McKnight paints a picture of a society where the Jesus Creed transforms life, which is Jesus’ own view of the Kingdom of God. McKnight reminds us that living this way, the way of the Jesus Creed, is not about hard work in order to arrive at perfection, but about relationship and growing in love. “The most potent incentive to spiritual formation" he writes, "is to see the end of history, to ponder God’s eternity, and to realise that this end shapes our beginning each day."

Publisher: Paraclete Press, Brewster, MA (2004)