Note 9 at 2 Cor. 6:17: It is possible that Paul is combining two Old Testament scriptures (2 Sam. 7:14 and Isa. 52:11) to come up with this promise. However, that is not clear. It is just as probable that this is a promise that he is uttering under the inspiration of the Holy Spirit at that moment.

Regardless of when it was inspired, it definitely is a promise of God's acceptance to those who separate themselves from the pollution of the world.

Note 10 at 2 Cor. 6:17: These verses are a plea from God for our separation from the world. The number one reason most people feel pressure to conform to the world is peer pressure or a fear of rejection. God didn't create mankind for rejection, and there is something innate within each of us that longs for acceptance. So, God promises us His acceptance if we will be separate unto Him. A person who is experiencing God's acceptance and pleasure will not miss the acceptance of the world.