THE INDIVIDUAL UNITS OF BOOK 4
Psalm 90, the first of a new "book" of Psalms, is the only one attributed to Moses. Why is this so? Perhaps the late collectors and editors of the psalms wanted to mark a new beginning of Israel, after the downfall of the monarchy, as a Torah-centered community (→ Psalm 89, Intention), or were dwelling on some affinities of Psalm 90 to the Song of Moses (Deuteronomy 32), or they simply thought of Moses as the most ancient hero of their history. He was closest to primeval antiquity, he was the most intimate with God (Exod 33:11); therefore he should have the best information about prehistoric times. The SUPERSCRIPTION, in consequence, names Moses "man of God," a title otherwise restricted to prophetical figures of the monarchic period. The psalm itself is classified tĕpillāh, "prayer," like Psalm 86 and only one more song in the Psalter (Psalm 102), perhaps because of basic human anxieties expressed throughout vv. 1–12.
A brief look at our psalm, however, suggests that the original text can be neither derived from Moses or his epoch nor interpreted as a petitionary prayer