Hosea 1:10 Yet the number of the children of Israel shall be as the sand of the sea, which cannot be measured nor numbered; and it shall come to pass, that in the place where it was said unto them, Ye are not my people, there it shall be said unto them, Ye are the sons of the living God.
This was a reminder from God through his prophet of His covenant with Abraham, Isaac and Jacob.
Gen 22:17 That in blessing I will bless thee, and in multiplying I will multiply thy seed as the stars of the heaven, and as the sand which is upon the sea shore; and thy seed shall possess the gate of his enemies;
Gen 22:18 And in thy seed shall all the nations of the earth be blessed;
The prophet speaks the mercy of God to the covenant people of God through Messiah, Jesus Christ. They will not be forgotten forever. One minister said that all Jews will be saved. Not until the end will they be saved. All Israel will be saved at the second coming of the Messiah Jesus, but those remaining after the tribulation will be fewer in number.
Rom 11:25 For I would not, brethren, that ye should be ignorant of this mystery, lest ye should be wise in your own conceits; that blindness in part is happened to Israel, until the fulness of the Gentiles be come in.
Rom 11:26 And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob:
Rom 11:27 For this is my covenant unto them, when I shall take away their sins.
Rom 11:28 As concerning the gospel, they are enemies for your sakes: but as touching the election, they are beloved for the fathers' sakes.
Rom 11:29 For the gifts and calling of God are without repentance.
I always saw this verse of the gifts and callings as referring to backslidden Christians. It primarily is referring to Israel. The gifts, plural, and the calling. God called them unto himself and finally when Jesus comes in the end times, they will hear his calling to them and be saved. When saved then they will receive the gifts for ministry. Some people on their death bed have said, "I know I was to be a missionary but I ran from God." What a sad thing to miss God. Come to Jesus and be strong in him, he is our refuge and strength and our gift giver.
Rom 11:30 For as ye in times past have not believed God, yet have now obtained mercy through their unbelief:
Rom 11:31 Even so have these also now not believed, that through your mercy they also may obtain mercy. Rom 11:32 For God hath concluded them all in unbelief, that he might have mercy upon all.
Rom 11:33 O the depth of the riches both of the wisdom and knowledge of God! how unsearchable are his judgments, and his ways past finding out!
Rom 11:34 For who hath known the mind of the Lord? or who hath been his counsellor?
Rom 11:35 Or who hath first given to him, and it shall be recompensed unto him again?
Rom 11:36 For of him, and through him, and to him, are all things: to whom be glory for ever. Amen.
Do not miss your time of salvation and service. Nothing is more miserable than to be outside of the blessings of God.