About that aorist imperative...

But the great strength and attractiveness of Paul's moral code is that all these practical changes in behaviour have a genuine and God-given basis; they are not changes which men must attempt in their own moral power, constantly working themselves up to do the impossible. There is a true emancipation from the old enslavements and a new power in the Spirit to lives as God desires (Rom. 8:1–8).

It is because of this factual basis of the Christian's new life in Christ that Paul is influenced to call upon Christians to make a definite practical break with the past and to begin to live in practice as new people. It seems that this ingressive idea is the motivation for several of the Pauline aorists listed earlier.—Verbal Aspect in New Testament Greek, pages 360–61 (emphasis original)