Being chosen to be God's special treasure and become holy had nothing to do with any of our accomplishments, race, nationality, gender, IQ, or academic training. We are special and thus blessed because God loves us and because He is faithful to His promises to the fathers, Abraham, Isaac, and Jacob. He reinforces these points by emphasizing that He is faithful, as well as by warning us that He is a God of justice.
Therefore, He is clearly stating that the foundation of this relationship is based completely in what He is within Himself, otherwise the relationship would have never gotten past the casual stage of mere acquaintance. The vast majority in the world who call themselves Christian are merely acquainted with God. By God's personal calling (John 6:44, 65), we have been made special—to have an intense and intimate relationship with Him. The very character of God, not any excellence in those He has chosen, is the basis for our being special.
This gives us no room for pride. He was not somehow attracted to us because we had been seeking Him all our lives, were so attractive, or had done so many good things. On the other hand, this blessing gives cause for a great deal of gratitude, and just as in a marriage, this specialness brings responsibilities.
God proclaims Himself to be the faithful God, and in Deuteronomy 7:11, He broadly states the means by which we are expected to prove our faithfulness in return: We are responsible to keep His commandments, statutes, and judgments. As in a marriage, because the parties have become special to each other, they are responsible to be faithful to each other above all others. A covenant made before God binds us to this intense, marital faithfulness.
I Peter 2:9 states this responsibility in a somewhat different manner: "But you are a chosen generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him, who called you out of darkness into His marvelous light." Notice his sentence begins with "but," introducing an explanation of why the chosen are to be different from the disobedient of verses 7-8, and of what they are obligated to do.
As stated here, the responsibility of God's own special people is to proclaim—to show forth (KJV)—the praises of Him who has called us. The proclaiming is accomplished through speech and conduct. We show forth His praises in our witness through faithful obedience, just as is commanded in Deuteronomy 7:11.
Therefore gird up the loins of your mind, be sober, and rest your hope fully upon the grace that is to be brought to you at the revelation of Jesus Christ; as obedient children, not conforming yourselves to the former lusts, as in your ignorance; but as He who called you is holy, you also be holy in all your conduct, because it is written, "Be holy, for I am holy."
God emphasizes "special treasure" to impress us with the magnitude of His blessing in making us special and the critical importance of our difference from others expressed through holy conduct.
It is important to consider our calling as God's peculiar treasure a tremendous blessing that we never allow to slip from our minds. It opens the door to the knowledge of God, faith, forgiveness, His Holy Spirit, access to Him, transformation to be like Him, and an endless supply of other things He provides, besides everlasting life. However, there are specific things we must do and cannot do because we are special.