T'hillim / Psalm 45:7 (6 in Christian versions which eliminate the first line or don't number it) says "Your throne, O judge (King David) [will] exist forever and ever; the scepter of equity is the scepter of your kingdom."
How is this a prophecy about Jesus?
How is this a prophecy about anything?
How can a statement about King David be claimed to be speaking of Jesus owning the title "G-d" (G-d forbid!)?
The psalm is speaking of King David and saying that King David's right to the throne will exist forever. It says nothing about the messiah being G-d (G-d forbid).
The promise that the rightful Jewish throne will always belong to King David through his son, Solomon, is repeated time and again in the T'nach. “And it will come to pass when your days (David) are finished to go with your forefathers, then I (G-d) shall raise up your seed after you, who will be of your sons, and I shall establish his kingdom.” Divrei Hayamim Alef / I Chronicles 17:11.
G-d is again speaking to David and He says “Behold a son will be born to you; he will be a man of peace, and I shall give him peace from all his enemies around about, for Solomon will be his name, and I shall give peace and quiet to Israel in his days. He shall build a House in My Name, and he shall be to Me as a son, and I to him as a Father, and I shall prepare the throne of his kingdom forever.'” Divrei Hayamim Alef / I Chronicles 22:9-10.
The message of Divrei Hayamim Alef / I Chronicles 17:11-12 is repeated in Divrei Hayamim Alef / I Chronicles 22:9-10 and this time Solomon is given by name. The information is the same:
Re-read the line in question, T'hillim / Psalm 45:7 (6 in Christian versions which eliminate the first line or don't number it) which says "Your throne, O judge (King David), [will exist] forever and ever; the scepter of equity is the scepter of your kingdom."
The "title" elohim does not equal G-d. The word אֱלֹהִים / elohim is used in the Jewish bible to speak of G-d, of false gods, of people (like judges) and angels. It is not exclusively used to speak of G-d. The term is used more than 2000 times in the T'nach -- often for humans or angels as well as for G-d.
Thus it is clear that the author of Hebrews 1:8 tries to hijack this line in T'hillim / Psalm 45:7 and apply it to Jesus (as if he was G-d), but he is lying to his readers - distorting the context and meaning of the psalm which is about a military king (King David). Jesus was neither a king, or a military man -- and more importantly the Hebrew word אֱלֹהִים / elohim does not always mean G-d. This is a mistranslation and misuse by the Christian bible as well as the list maker.
In Shmuel Beit / 2 Samuel 7:23 the word אֱלֹהִים / elohim denotes “emissaries sent by G-d” (Moses and his brother Aaron), based on Sh'mot / Exodus 7:1 "The L-rd said to Moses, "See! I have made you a lord / אֱלֹהִים / elohim over Pharaoh, and Aaron, your brother, will be your speaker." Many missionaries mistranslate Shmuel Beit / 2 Samuel 7:23 to try to indicate a trinity. For example, Jews for Jesus says "…G-d (Elohim) went…" [Literally: They went.]." They then use this to say that "they" (plural) means a triune god -- a trinity. Could it be just a coincidence that missionaries like Jews for Jesus cut the quote off after the word “went....” and deliberately refrain from mentioning what follows “....to redeem them FOR HIMSELF as a nation and to establish a reputation FOR HIMSELF....”? (singular). Shmuel Beit / 2 Samuel 7:23 the word אֱלֹהִים / elohim denotes “emissaries sent by G-d” -- not a triune god, and by mistranslating elohim as a plural god the missionaries mislead their readers.
Rashi opines (regarding Shmuel Beit / 2 Samuel 7:23) whom G-d went: Moses and Aaron, as it is written: “I have made you a ruler over Pharaoh” (Exod. 7:1). Now this is also Jonathan’s interpretation; “whom messengers of G-d went…”
to redeem to Himself a people: This the messengers said to the Israelites.“The Holy One blessed is He sent us to redeem to Himself a people, and to make to Him a name, and to accomplish for you the greatness.”
Other instances showing that elohim is used to speak of others than G-d include B'reshit / Genesis 32:29 most Christian translations (verse 28 in Christian versions) say that Jacob wrestled with G-d, translating אֱלֹהִים / elohim as G-d. This is a mistranslation as is easily discovered by reading the prophet Hosea who tells us that Jacob wrestled with an angel, not G-d. Hoshea / Hosea 12:5 "He (Jacob) strove with an angel and prevailed; he wept and beseeched him; In Bethel he shall find Him, and there He shall speak with us."
Hosea proves that the אֱלֹהִים / elohim (powerful judge) with whom Jacob wrestled was not G-d, but was an angel.
Mistranslations mislead -- this false prophetic claim that Jesus would be "own the title of G-d / elohim" is based on an ignorance of Hebrew that this word, although used to speak of G-d, is not exclusively a name for G-d. The word אֱלֹהִים / elohim is used to speak of angels, false gods, humans and G-d Himself. Read in context in the psalm it is clear that the author is speaking of King David whose line was destined to be the rightful kings of Israel and the ancestor to the eventual real messiah.