Spiritually, this passage is every bit as stringent as Deuteronomy 7:1-5, and the reasons are the same: We are holy. Our holiness must be protected from contamination, perfected through the relationship with God (not with this world), and growing in living God's way of life. Paul's words are a stern warning not to get close to the world.
Paul asks five rhetorical questions in these verses to show that God's way has nothing in common with the world. Nothing! In verse 17, Paul quotes Isaiah 52:11, showing that our acceptance by God depends upon obedience, which is loyalty to Him. His statement about cleansing ourselves shows a continuous action. It is not written in Greek as it appears here in English. If it would have been translated as Paul wrote it, the verse would show that cleansing ourselves is a responsibility that must be carried out every day!
Two of God's festivals are devoted to reminding us of this responsibility, one in the spring and one in the fall. At Passover, in the spring, we partake of footwashing; we are to have our feet washed once a year because we become symbolically dirty as we walk through life. We do not always walk as we should, so we must be cleansed. How long do you think it would take for us to begin forgetting such things if we no longer kept Passover and its ritual of washing one another's feet?
Every fall, before we keep the Feast of Tabernacles, we experience another cleansing on the Day of Atonement, the internal cleansing of a fast, which is what a fast does to a body physically. It begins to dump its garbage through the bowels and the urinary tract. Every cell in the body begins to work in reverse and cast off the garbage within them.
It is interesting that at Passover, the symbol is external, but on Atonement the symbol is internal. Keeping ourselves clean is important to God; He gives us reminders to do so twice a year! He wants us clean on the outside and on the inside. He wants us clean in what we believe, and He wants us clean in our external conduct. Our hearts must be cleansed as does our behavior.
Thus, II Corinthians 7:1 indicates a daily cleansing, a daily repentance. Paul writes in I Corinthians 15:31, "I die daily." This daily dying to sin—cleaning up his act, as we say—is what he meant.
