Heb 1:8-9, Gen 49:10, Isa 9:6-7, Lk 1:31-33

In the Old Testament it was foretold that the coming Christ would be over all kings. (Psalms 45:6-7)

Psalms 45:6 Thy throne, O God, is for ever and ever: the sceptre of thy kingdom is a right sceptre. 7 Thou lovest righteousness, and hatest wickedness: therefore God, thy God, hath anointed thee with the oil of gladness above thy fellows.

The Old Testament prophesied that Christ would come as a descendant of Judah and would become the eternal king. (Gen 49:10)

Gen 49:10 The sceptre shall not depart from Judah, nor a lawgiver from between his feet, until Shiloh come; and unto him shall the gathering of the people be.

The Old Testament spoke of the coming of the Son of God as the eternal King, King of kings. (Heb 1:8-9, Isa 9:6-7)

Heb 1:8 But unto the Son he saith, Thy throne, O God, is for ever and ever: a sceptre of righteousness is the sceptre of thy kingdom. 9 Thou hast loved righteousness, and hated iniquity; therefore God, even thy God, hath anointed thee with the oil of gladness above thy fellows.

Isa 9:6 For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace. 7 Of the increase of his government and peace there shall be no end, upon the throne of David, and upon his kingdom, to order it, and to establish it with judgment and with justice from henceforth even for ever. The zeal of the Lord of hosts will perform this.

Jesus is the Christ, the eternal King who came as a descendant of Judah and David. (Luke 1:31-33, Matthew 1:16)

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.