Moses
Psalm 89:19BSB·traditional attribution

You once spoke in a vision; to Your godly ones You said, “I have bestowed help on a warrior; I have exalted one chosen from the people.

John Calvin Reformed @genevareformer

PSALM 89 The prophet who wrote this psalm, whoever he was, in approaching the throne of grace to make supplication to God in behalf of the afflicted Church, lays down, as an encouragement both to himself and the rest of the faithful to cherish good hope, the covenant which God had made with David.

Commenting on Psalm 89:1-52

C.H. Spurgeon Reformed Baptist @princeofpreachers

Then thou spakest in vision to thy holy one. The Psalmist returns to a consideration of the covenant made with David. The holy one here meant may be either David or Nathan the prophet, but most probably the latter, for it was to him that the word of the Lord came by night. 2Sa 7:4-5.

Matthew Henry Presbyterian @wholebiblehenry

The covenant God made with David and his seed was mentioned before (Psa 89:3, Psa 89:4); but in these verses it is enlarged upon, and pleaded with God, for favour to the royal family, now almost sunk and ruined; yet certainly it looks at Christ, and has its accomplishment in him much more than in David; nay, some passages here are scarcely applicable at all...

Commenting on Psalm 89:19-37