Mt 1:1, Lk 1:31-33, Rom 8:29, Heb 1:5-6
In the Old Testament, the psalmist confessed that God would give an eternal throne to the descendants of David. (Psalm 132:11-12)
Psalm 132:11 The Lord hath sworn in truth unto David; he will not turn from it; Of the fruit of thy body will I set upon thy throne. 12 If thy children will keep my covenant and my testimony that I shall teach them, their children shall also sit upon thy throne for evermore.
Jesus is the Christ who has received the kingship of David forever, who came as a descendant of David. (Matthew 1:1, Luke 1:31-33, Matthew 1:16)
Matthew 1:1 The book of the generation of Jesus Christ, the son of David, the son of Abraham.
Luke 1:31 And, behold, thou shalt conceive in thy womb, and bring forth a son, and shalt call his name Jesus. 32 He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David: 33 And he shall reign over the house of Jacob for ever; and of his kingdom there shall be no end.
Matthew 1:16 And Jacob begat Joseph the husband of Mary, of whom was born Jesus, who is called Christ.