Why does God refer to Jerusalem as his daughter?
The first reference to Jerusalem as a daughter occurs in the Psalms. Psalm 9:13, 14 says, "Have mercy upon me, O LORD; consider my trouble which I suffer of them that hate me, thou that liftest me up from the gates of death: That I may shew forth all thy praise in the gates of the daughter of Zion: I will rejoice in thy salvation." The phrase, "daughter of Zion" is a poetic phrase used to symbolize the relationship between God and his people. The phrase is used at least fifty times in the Old Testament to refer to God's people. However, the word "daughter" is sometimes used to describe other nations as well as in "daughter of Egypt" or "daughter of Babylon." Usually in these cases it is simply referring to the nation itself. Sometimes the context in which the phrase is used refers to God's people in a favorable way and sometimes in an unfavorable way. The emphasis, however, is not upon the people themselves, but the relationship that they have with God--one of a Father and daughter. The phrase is mostly found in the prophets. Out of all of the prophets, Jeremiah uses it the most. The poetical context of the book of Lamentations is replete with the phrase.
We get more information about this metaphorical relationship between God and his people in Ezekiel 16. Here, God describes his people as a female child that had been tossed out in an effort of abortion. Abandoned, rejected, naked, cold, and still bloody, God rescued this child from a likely death. Ezekiel then describes God as raising the child, clothing the child, and even providing a permanent household for the child. On top of this, God gave this child clothing and raiment and jewelry and held nothing back for her profit. The result was that this young child grew into a beautiful woman. However, the response of the woman once she was grown was to trust in her own beauty and play the harlot, rejecting the one who had rescued her and blessed her with so many great and wonderful things.
In the New Testament, Jesus refers to the people of Jerusalem as God's daughter in Matthew 21:5. This is from a prophecy in Zecheriah 9:9. The prophecy is related to the triumphal entry of the Messiah into the city of Jerusalem and in this context the phrase refers to the people of Jerusalem. Today, the daughter of God is the church. She is the bride of Christ (Eph.5:21ff). She will be presented to Jesus in heaven without spot and blameless (Revelation 21:2, 9).
There is another point that I would like to make in regard to this particular metaphor. God speaks to us in terms that we can understand. We can understand the metaphor of the relationship between a father and daughter and so we learn a little more about God and who He is by understanding that relationship. The Bible uses this type of language frequently. We refer to it as accommodative language--language that uses terms and illustrations that we can understand so that God can teach us lessons. This is one of the reasons why Jesus spoke in parables. He used terms that we can understand. God makes every effort on his part to try to communicate with us in ways that we can understand.
There are some today who say you can't understand the Bible. That it is too difficult and too hard. These metaphors and illustrations stand as a testimony against those who say such. God wants us to understand His word and speaks to us in ways that we CAN understand His word. The problem is usually on our part--that we simply do not want to hear. In a beautiful illustration of this very point, Moses says to the children of Israel, "For this commandment which I command thee this day, it is not hidden from thee, neither is it far off. It is not in heaven, that thou shouldest say, Who shall go up for us to heaven, and bring it unto us, that we may hear it, and do it? Neither is it beyond the sea, that thou shouldest say, Who shall go over the sea for us, and bring it unto us, that we may hear it, and do it? But the word is very nigh unto thee, in thy mouth, and in thy heart, that thou mayest do it" (Deut.30:11-14). What will your response be to God's word today?