The young woman is involved in a marriage. Within the context, she begins as a type of Jerusalem and gradually expands into a type of all Israel. Within the fullness of the Bible, the symbolism can apply all the way to include the church and the New Covenant. Verse 8 clearly states, "You became Mine."
The statement, "I spread My wing over you," is a symbol of caring protection. It can also imply what Boaz did in accepting Ruth when, at Naomi's bold suggestion, she came to him at night and slept at his feet. Ruth was willing to pay the price of possibly losing her reputation by being perceived as a prostitute because the community could have interpreted what she did as brazenly throwing herself at Boaz. But Boaz, being a just man (also a type of Christ), took the hint properly and redeemed Ruth to be his wife. "I spread My wing over you" suggests both as a companion in marriage and as a possession.
The Old Covenant was a marriage covenant, and it prefigures the New Covenant, which is also a marriage covenant. Several verses confirm that the church as Christ's Bride is a purchased possession. The apostle Paul writes in I Corinthians 6:19-20: "Or do you not know that your body is the temple of the Holy Spirit who is in you, whom you have from God, and you are not your own? For you were bought at a price; therefore glorify God in your body and in your spirit, which are God's" (see also I Corinthians 7:22-23; II Peter 2:1). These verses are especially clear regarding the legal realities involved in this relationship. The price of our redemption from slavery to Satan and this world has been paid by Christ when He shed His blood. We legally belong to Him.
John W. Ritenbaugh
Fully Accepting God's Sovereignty (Part Two)
God is describing His relationship with a specific woman, Jerusalem, which stands for all Israel. In this context, "you became Mine" is the language of marriage, a covenant relationship to One to whom she was to be faithful.
John W. Ritenbaugh
The Beast and Babylon (Part Five): The Great Harlot