I once had this profound thought about the grace of God while thinking about airplanes. The thing about planes is that we never see one with only one wing on one side. They always have to have two wings sticking out to the left and to the right.
The reason behind that is the same reason why we often have this urge to stick out both our arms when we try to balance over a sidewalk, a line or a beam. The two wings of a plane provide balance for the whole craft. When a plane only has a wing, you'll be sure that the plane will start spinning out of control.
The grace of God is the same way - it needs balance and thus has to have two "wings" so to speak. One wing is justification while the other is sanctification. We need to understand both to get a good grasp of the grace of God. When we have only one of both, then we start spiralling out of spiritual control. Here are two ways we get the grace of God wrong.
The absence of justification: Legalism
Legalism at it's root is an attitude that declares, "I have to." When we feel that we have to read the Bible, to tithe, to build discipline, to make things right in order to earn God's favor, we are missing the wing of justification that tells us that because of what Jesus has accomplished on the cross, we are now favored by God simply by faith.
This is what Ephesians 2:8 refers to when it says, "For by grace you have been saved through faith. And this is not your own doing; it is the gift of God."
The absence of sanctification: Rebellion
While legalism says "I have to," rebellion declares "I won't/I can't." When we miss out on God's sanctifying power, we reduce grace to a crutch that now allows us to sin without consequence. But God sanctifies us as the Holy Spirit teaches us to renounce sinful patterns in our lifestyle.
Titus 2:11-12 says it best: "For the grace of God has appeared, bringing salvation for all people, training us to renounce ungodliness and worldly passions, and to live self-controlled, upright, and godly lives in the present age."
The proper response
Having both wings of justification and sanctification leads us to respond this way: "I can't, but Jesus has so I will." Understanding grace starts with understanding that because we are sinful people, there is a long list of things we cannot accomplish. But what we cannot do on our own, Jesus has done for us.
He has saved us from our transgressions, provided us with security and identity and now gives us a new hope and new life. This then compels us to live in a certain way - the way God commands us to live. We live not based on what we feel we are to do for God to love us or to refuse to try, but are instead compelled now to act as our response to God's love.
