The dominant mode of evangelical preaching on sanctification, the main way to motivate for godly living, sounds something like this:
You are not _____;
You should be _________;
Therefore, do or be ________!
Fill in the blank with anything good and biblical (holy; salt and light; feed the poor; walk humbly; give generously; etc.).
This is not how Paul and the other New Testament writers motivated the church in light of the resurrection and the outpouring of the Spirit. They did give imperatives (=what you should do), but they do so only based on indicatives (=what God has done).
The problem with the typical evangelical motivation toward radical or sacrificial living is that “imperatives divorced from indicatives become impossibilities” (to quote Tullian Tchividjian). Or another way that Tullian puts it: “gospel obligations must be based on gospel declarations.”
This “become what you are” way of speaking is strange for many us us. It seems precisely backward. But we must adjust our mental compass in order to walk this biblical path and recalibrate in order to speak this biblical language.
We see this all throughout the NT. Here are a few examples of this gospel logic and language:
“You really are unleavened” (indicative),
therefore “Cleanse out the old leaven that you may be a new lump” ( imperative). [1 Cor. 5:7].
“You are not under law but under grace” and you “have been brought from death to life (indicatives),
therefore “Let not sin therefore reign in your mortal body. . . .
Do not present your members to sin as instruments for unrighteousness,
but present yourselves to God as those who have been brought from death to life, and your members to God as instruments for righteousness” ( imperatives). [Rom. 6:12-14]
“Having been set free from sin, [you] have become slaves of righteousness (indicatives) . . .
[therefore] now present your members as slaves to righteousness leading to sanctification (imperative). [Rom. 6:18-19]
“Those who belong to Christ Jesus have crucified the flesh with its passions and desires” (indicative),
therefore, “walk by the Spirit, and you will not gratify the desires of the flesh” ( imperative). [Gal. 5:16, 24]