I will sow her to me in the earth; And I will have mercy on her who had not obtained mercy; And I will tell those who were not my people, 'You are my people;' And they will say, 'My God!'"
"That had not obtained mercy ..." This verse also is a bold and definite prophecy of the receiving of the Gentiles into the New Covenant. Paul quoted both this verse and  Hosea 1:10 in  Romans 9:25-26, applying both passages to the current dispensation of Christ.  For the same purpose, Peter also used the terminology of both these passages in  1 Peter 2:10. Thus, there can be no valid question of the Messianic import of this remarkable prophecy.