But the Lord's portion is his people.Deuteronomy 32:9
How are they His? By His own sovereign choice. He chose them and set His love upon them. He did this completely apart from any goodness in them at the time or any goodness that He foresaw in them.
He had mercy on whom He would have mercy and ordained a chosen company to eternal life; in this way, therefore, they are His by His unconstrained election.
They are not only His by choice, but by purchase. He has bought and paid for them completely, and so there can be no dispute about His title.
Not with corruptible things like silver and gold, but with the precious blood of the Lord Jesus Christ, the Lord's portion has been fully redeemed.
There is no mortgage on His estate; no lawsuits can be raised by opposing claimants. The price was paid in open court, and the Church is the Lord's estate forever. See the blood-mark upon all the chosen, invisible to the human eye but known to Christ, for "the Lord knows those who are his."1
He forgets none of those whom He has redeemed from among men; He counts the sheep for whom He laid down His life and remembers carefully the Church for which He gave Himself.
They are also His by conquest. What a battle He had in us before we would be won! How long He laid siege to our hearts! How often He sent us terms of surrender, but we barred our gates and built our walls against Him.
Do we not remember that glorious hour when He carried our hearts by storm, when He placed His cross against the wall and scaled our ramparts, planting on our strongholds the blood-red flag of His omnipotent mercy? Yes, we are indeed the conquered captives of His omnipotent love. As those chosen, who have been purchased and subdued, we know that the rights of our divine possessor are inalienable: We rejoice that we can never be our own; and we desire, day by day, to do His will and to declare His glory.
1) 2 Timothy 2:19