At an auction for some very rare and precious collectibles, two bidders were “going at it.” The older bidder, unknown to everyone else in the room, had snatched one of the most valuable pieces in the auction, which really irked a young “opponent.” Determined to “stick it to” the old man, the young hot head ran up the bid on the final item, which the old man eagerly desired. The young bidder won the item, spoiling the old man’s pursuit. In reality, the young man did not want the item at all (and later got rid of it); he just wanted to keep it away from the old man.
That story comes to mind when considering one significant word in Acts 20:28. The Bible says that the Lord purchased the church with His own blood. Did He purchase it just to keep it away from someone else? 
Did He purchase it while knowing that He didn’t really want it for Himself? No and no! The Greek word (in the middle voice) emphasizes that Jesus acquired, preserved, purchased the church for Himself! The emphasis of the middle voice is on the action being done by or for Himself! Christians are “God’s own possession” (1 Pet. 2:9, ASV).