a holding of something as one's own, whether by keeping it safe or by gaining it, and by extension the treasured thing so held
This word is built from a verb meaning roughly to make something remain, and to keep it for oneself. From that one idea three shades grow, and which one a passage carries depends on the words around it. When the thing at stake is a life, it means keeping that life safe. When the thing is a good still to be gained, it means obtaining. When the word names a group of people who now belong to God, it means his treasured possession.
These are not three separate words but one word seen from different angles. To obtain something and then to own it are the front and back of a single act: God obtains a people, and that people is now his possession. Keeping safe and obtaining also shade into each other when what is at stake is rescue on the day of judgment, where to gain one's life and to hold on to it come to nearly the same thing.
In two places, Ephesians and 1 Peter, the word carries an extra weight from the Hebrew Scriptures. There God called Israel his own treasured possession (סגלה), a people he set his heart on and made his own, and the Greek Old Testament rendered that phrase with this very word in Malachi. So when the New Testament calls the church God's possession, it is claiming for believers the name once given to Israel. That richer meaning comes from the surrounding quotations, not from the bare word on its own.
Nuances
Whether the phrase "a people for his possession" means a people God owns as his treasured possession, or a people destined to be preserved and vindicated at the end.
- majorityA people that are God's own possession, echoing the Old Testament designation of Israel as God's treasured people (Malachi 3:17).; John H. Elliott, 1 Peter (Anchor Yale Bible 37B), 435-439; Paul J. Achtemeier, 1 Peter (Hermeneia), 164-165; Karen H. Jobes, 1 Peter (Baker Exegetical Commentary on the New Testament), 161-163
- minorityA people destined for preservation and vindication in the end, keeping the active verbal sense found in Paul.; J. Ramsey Michaels, 1 Peter (Word Biblical Commentary 49), 109
Whether "the redemption of the possession" refers to God's own people, whom he has acquired as his treasured possession, or should be rendered "remnant".
- majorityThe redemption of God's own people, whom he has acquired as his treasured possession, sealed by the Spirit (echoing Malachi 3:17).; Harold W. Hoehner, Ephesians: An Exegetical Commentary (Baker Academic); Peter T. O'Brien, The Letter to the Ephesians (Pillar New Testament Commentary); Andrew T. Lincoln, Ephesians (Word Biblical Commentary 42)
- minorityThe word here means "remnant" rather than "possession".; Frank Thielman, Ephesians (Baker Exegetical Commentary on the New Testament), 84-86