Paul builds on the model of Jesus (vs 6–11), drawing implications for his hearers: ‘Therefore’ (v 12). As Jesus obeyed his Father, believers are called to obey, for that it is where God’s power and blessing come. They aren’t doing this to earn their salvation, in the sense of belonging to Christ now and at the judgement day – but they are working out their salvation. They are walking on the Christian path, and aren’t alone, for as they walk in obedience to God, God does two remarkable things (v 13). He both directs their wills in his paths and gives them power to act in tune with his purposes.

After such amazing words, we come to earth with a bump in Paul’s call not to grumble or argue (v 14). This is where the rubber hits the road. Paul has the grumpy Israelites in the wilderness in mind, echoing Deuteronomy 32:5 (v 15). Churches can be, and are, split by negative speech – words can do enormous damage to others. The tongue is like a fire which can burn down a forest (James 3:5,6), but Christian speech is to shine with the light of God’s Word (vs 15,16).