אֲסַפְּרָ֗ה אֶֽ֫ל חֹ֥ק יְֽהוָ֗ה אָמַ֘ר אֵלַ֥י בְּנִ֥י אַ֑תָּה אֲ֝נִ֗י הַיּ֥וֹם יְלִדְתִּֽיךָ׃
לאָמיר דערצײלן פֿון דער באַשערונג:גאָט האָט מיר געזאָגט: מײַן זון ביסטו, איך האָב הײַנט דיך געבאָרן.
Rashi
I will tell of the decree Said David, “This is an established decree, and [one] that I have received to tell this and to make known.”
Radak
Let me declare it for a decree: – This is the utterance of David, who says, I will make this declaration a decree and rule. And what is the declaration? That
Ibn Ezra
Let me tell (אֲסַפְּרָ֗ה - asapperah): These are the words of David along with his prophecy; or, the words of the poet [who composed the psalm] speaking on his [David's, or the Messiah's] behalf.
Rashi
You are My son The head over Israel, who are called “My firstborn son.” And they will endure through you, as is stated concerning Abner (II Sam. 3:18): “for God said, etc., ‘By the hand of My bondsman David shall I deliver...Israel.’” And for their sake, you are before Me as a son because they are all dependent upon you.