Hosea married Gomer. Evidently she left him in an adulterous relationship for the advantages' of another man. God tells Hosea to go take her back.
Hosea had to buy her back. 15 shekels was half the price of a slave. 1 and 1/2 homer of barley= 45 bushels. The fond allowance for a slave by the Romans was 4 bushels a month. Barley was the offering for one accused of adultery.
V. 3. For many days she was to sit desolate. This was a picture of Israel. God delivered them, bought them out of Egypt. They went a whoring after other gods, adultery and were taken into slavery.
They were brought back and are now dwelling without these things mentioned in v. 4. Might mention there is no way the proper sacrifice can be reinstituted. First, the line of Aaron is forever lost never to be recovered. Second, the Messiah has come which also forever put the end to this sacrifice.
V. 5. --and David-- See my notes on Ezek. 34:23, 24, etc. This must be speaking of Christ because David is forever in the grave.
Latter days-- See Peter's statement in Acts 2:17 (also Heb. 1:2). The last days then always speaks of the last period of time from the coming of the Messiah on. We are living in them according to Peter.
Here in v. 5, we have the true Israel seeking after the David of the last days, Jesus Christ our Lord, Ps. 110:1.
Rom. 9, along with many other passages, the true Israel has always been one of faith in the Messiah and it still is.
David their king. Read this book of Matthew where it talks of the kingdom of God, kingdom of heaven, etc. You can't have a kingdom without a king and our king is Jesus, the son of David.
The true Israel has always been the ones who have submitted to the KING. Spend a little time in research and you will have more passages to prove this than you can look up.
Shall fear-- The Holy Spirit puts His fear in our hearts. The natural man does not fear God and has no desire to fear Him. This is a work of grace which is taking place in these last days.
Might mention here, we cannot be dogmatic with prophecy. It is only a dim shadow. You cannot know the truth about a shadow until you see the real thing.
This could all be quite different than what it seems, but to me it fits well with scriptures as we leave them IN THEIR CONTEXT.
(For an excellent treatment of this see Barnes' notes, Minor Prophets I, pg. 13, of introduction.)