Ibn Ezra

Of me (לְנַפְשִׁי - le-nafshi, lit. "to my soul"): [The Lamed prefix means] "concerning" my soul/me. [This usage is] similar to (Exodus 14:3) "And Pharaoh will say concerning (li-) the children of Israel..." [and (Genesis 20:13)] "Say of (li) me, 'He is my brother.'" His deliverance (יְשׁוּעָתָה - yeshu'atah): [This form contains] two signs of the feminine gender [the linking Tav (ת) and the final Heh (ה)], used by way of elegance/poetic expression. Examples are 'eimatah' (אֵימָתָה - his terror) [as in (Exodus 15:16): "תִּפֹּל עֲלֵיהֶם אֵימָ֫תָה וָפַ֫חַד" - "Terror and dread fall upon them"] and 'ba-tzaratah' (בַּצָּרָתָה - his distress) [as in (Psalm 120:1): "אֶל־יְ֭הוָה בַּצָּרָ֣תָה לִּ֑י קָ֝רָ֗אתִי" - "To the LORD, in my distress, I called"]. And [regarding the syntax of the verse itself], [the verse] mentions concerning his [David's] soul [נַפְשִׁי - nafshi, a feminine noun] using the masculine pronoun 'lo' (לוֹ - for him), similar to [the construction in (Isaiah 32:6)]: 'l'harik nefesh ra'ev' (לְהָרִיק נֶפֶשׁ רָעֵב - 'to make empty the soul [feminine noun] of the hungry [masculine adjective]')." Selah (סֶלָה): Many interpret Selah as "forever/eternally" (le-netzach), but this is not correct (ve-eineno nakhon). And the Aramaic translator (Targum) of the Book of Psalms [working] for others said: That the word Selah has no [inherent semantic] meaning (ta'am), but rather it is for regulating the musical intonation (tikkun ta'am ha-niggun). The proof [cited for this view] is that this word is not found anywhere in the Scripture except in the Prayer of Habakkuk [chapter] three, which is in the manner of Psalms, [written] al shigyonot [a musical term], similar to (Psalm 7:1) "Shiggayon of David," [and various psalms] "For the Leader; with stringed instruments" (La-menatzeach bi-nginotai). [However, Ibn Ezra notes a contradiction or complication with the Targum's usage:] Behold, the interpretation [given by the Targum] will be Selah = "forever" (le-netzach) [in practice, despite the claim it has no meaning]. Yet it is written concerning the waters of Meribah [in (Psalm 81:8)], "Selah", and [this interpretation is problematic because] the strife was only once. Also it is written (Habakkuk 3:3) "and the Holy One from Mount Paran. Selah." And the correct [view] is that the meaning of Selah is like: "So it is," or "Thus," and "The matter is true and correct." [It serves as an affirmation of the preceding statement].