John Calvin Commentary Hosea 2:1

"Say ye unto your brethren, Ammi; and to your sisters, Ruhamah." — Hosea 2:1 (ASV)

The Prophet having spoken of the people’s restoration, and promised that God would in time receive into favor those whom he had previously rejected, now exhorts the faithful to mutually stir up one another to receive this favor. He had previously mentioned a public proclamation, for it is not in the power of men to make themselves the children of God, but God himself freely adopts them. But now the mutual exhortation of which the Prophet speaks follows the proclamation, for God at the same time invites us to himself. After we are taught in common, it then remains that each one should extend his hand to his brothers, that we may thus with one consent be brought together to the Lord.

This then is what the Prophet means by saying, Say to your brothers, עמי omi, and to your sisters רוחמה ruchamah; that is, since I have promised to be propitious to you, you can now safely testify this to one another. We then see that this discourse is addressed to each of the faithful, that they may mutually confirm themselves in the faith, after the Lord will offer them favor and reconciliation.