Psalm 89:5-7 employs Ancient Near East language of a court of the gods in heaven. Or more accurately the court of One God, since Jewish religion is strictly monotheistic. So in this court there is one God, YHWH, and a surrounding court of courtiers, much like the court of an absolute monarch on earth.
5 Let the heavens praise your wonders, O Lord,
your faithfulness in the assembly of the holy ones!
6 For who in the skies can be compared to the Lord?
Who among the heavenly beings is like the Lord,
7 a God greatly to be feared in the council of the holy ones,
and awesome above all who are around him?
Verse 5 mentions the “in the congregation of the saints” (Hebrew בִּקְהַל קְדֹשִֽׁים be qahel qadoshim ; Septuagint ἐν ἐκκλησίᾳ ἁγίων) which is taken by many readers to be angels, rather than men and women praising God on earth. And then in verse 6 we have “among the sons of God” (Hebrew בִּבְנֵי אֵלִים be bene elohim : Septuagint ἐν υἱοῖς θεοῦ ). And in verse 7, back to a near repeat of verse 5 (Hebrew בְּסוֹד־קְדֹשִׁים be sod qadoshim ; Septuagint ἐν βουλῇ ἁγίων).
The question is how much of this is literal, and how much is poetic. The Psalms, and all of the Bible, take the position that God has a court in heaven of heavenly ‘messengers (Hebrew malakim, Greek angeloi, messengers), but there are no instances in the Bible of these messengers daring to offer opinions or advice to God except two famous ones:
Firstly the highly sarcastic lampoon of the 300 lying prophets in the court of Ahab by the honest prophet Micaiah in 1 Kings 22:22. In Micaiah’s scurrilous prophecy one of the Sabbaoth, the heavenly Hosts, or Armies, steps forward to answer God’s call for a volunteer to “entice Ahab, that he may go up and fall at Ramoth-gilead?’
Secondly the very famous throne room scene in Job 1, which is probably partly based on Micaiah’s parody, as well as on more general exilic exposure to Babylonian cosmology. In Job 1 an Accuser-Courtier with case by case delegated powers from God comes among the Sons of God, to hear God’s praise of Job, only to answer God back and challenge God’s praise for Job.
But here in Psalm 89 there is none of that theatre and parody, just the poetry of praise. The phrase “council” in verse 7 does not suggest saints or angels giving God advice as the Micaiah and Job 1 stories contain, merely worship. Just as in verse 12 Tabor and Hermon rejoice in God’s name. No one has yet suggested that Tabor and Hermon are spirit beings who answer God’s call for a volunteer in Micaiah’s parody, or a heavenly courtier sceptical at the motives of men.
So is it literal? Strictly no. No more than Tabor and Hermon rejoicing. It’s a poem, more specifically a song. But the fact that it’s not literal doesn’t mean that God doesn’t literally have a court of angels praising Him in heaven, just as he literally has men and women praising Him on earth, and will do so more in the prophetic future for man and earth revealed in so many of the prophets.