Putting diesel in a petrol engine

As a Christian do you find it hard to see how the gospel inspires and motivates your life as a Christian?

We see how the gospel affects our justification (our legal standing before God) but we struggle to see how it shapes our sanctification (how we live for God).

But it really matters. Asking what motivates or drives your Christian life is like asking what fuel to put into a car engine. Petrol engines are designed to run on petrol, put the wrong fuel in the engine and try to drive on regardless you will very soon find yourself in serious problems.

Maybe one key insight from Martin Luther will help us.

The default position even of the Christian, left to ourselves, is to find our confidence and joy in the Christian life from our performance in the Christian life. It could come from how strong we feel our faith is, how bold we have been in speaking for Christ, whether we have yielded to temptation or not or a whole host of other performance indicators. When we do that we are saying to ourselves my faith is the thing that justifies me rather than God’s grace.

We subtly swap ‘my faith’ for ‘God’s grace’ and find ourselves looking in the mirror of our own performance. When we do that it’s like putting diesel in a petrol engine.

But here is Luther’s insight. Our faith is not our fuel. Faith is simply the means (the instrument) by which we grasp hold of our justification. Our faith is not the grounds of our justification.

Martin Luther said

It is, of course, true that I and you do not hold and believe the saving truth so firmly as St. Peter does. Yet we have one and the same treasure. Two persons may hold glasses of wine in their hands: the hand of the one trembles, the hand of the other does not. Two persons may hold a purse full of money: one with a weak hand, the other with a strong hand. Whether the hand is strong or weak, please God, it neither increases nor decreases the contents of the purse…

To bring the analogy into the 21^st century imagine two passengers on board a plane.  One is totally assured, completely confident that this plane is going to get off the ground, the other a nervous wreck who can’t see how it’s possible to keep 163 tonnes in the sky.  Which one of them is going to make it to their destination? Does the strength of their faith in the plane change anything? No. What matters is the strength of the plane and that weak or strong that each of them is on the plane.

What matters then is not the strength of our faith but that our faith exists at all!

How does that change things?

It teaches me that each day I need to place my trust not in my performance for Jesus but Jesus’ performace for me. Like filling up at the petrol station I need to pay very careful attention to which fuel I put into my Christian life.

If I fill up on ‘God’s gospel’ I drive off into the day assured of God’s love, confident in his grace and with a renewed joy I determine to serve him in the strength he provides.

If I fill up on ‘my faith’ I drive off into the day trying hard to please God, trusting in my own abilities and with a fear that I may not live up to God’s exacting standards.

It makes all the difference in the world.

No wonder  Luther also said:

‘Most necessary is [the gospel] that we know it well, teach it to others, & beat it into their heads continually’.

The doctrine of justification is a life-changing one – when we grasp it and live by it. It transforms our relationship with God, it revolutionises our service of God and it inspires total dedication to God!

Remember that will you the next time you fill up the engine.