Psalm 145 is an acrostic Psalm, which means that it is arranged alphabetically, according to the letters of the Hebrew alphabet.
The Masoretic Text for Psalm 145 does not have a verse that begins with the Hebrew letter nun, however. The Septuagint of Psalm 145 has what may have been the nun-verse that would later drop out. It states: “The LORD is faithful in his words, and holy in all his works” (Brenton’s translation). According to Leslie Allen, this also appears in the Syriac and 11QPs-a (which has “Elohim” for God rather than “YHVH”), and E.W. Bullinger states that it is present in the Arabic, the Ethiopic, the Vulgate, and a Hebrew codex. Meanwhile, the Targum, apparently following what would become the MT, lacks the nun-verse.
There is discussion within rabbinic literature about why the nun-verse is absent from Psalm 145. I learned about this from Chaim Pearl’s “The Theology of Psalm 145: Part II,” which appeared in the Winter 1991-1992 Jewish Bible Quarterly. This discussion is in Babylonian Talmud Berachot 4b. A reason that was advanced for why there was no nun-verse in Psalm 145 was that Psalm 145 is a positive Psalm, so it was deliberately omitting Amos 5:2, which starts with a nun. Amos 5:2 conveys a message of apparent hopelessness: “The virgin of Israel is fallen; she shall no more rise: she is forsaken upon her land; there is none to raise her up” (KJV). The verse starts with the Hebrew word naphelah, “she fell.”
According to Pearl, an epilogue to the Talmudic discussion stated that David included v 14 to compensate for the absence of the nun-verse. Psalm 145:14 affirms: “The LORD upholdeth all that fall, and raiseth up all those that be bowed down” (KJV). Psalm 145:14 contains the word n-ph-l (“fall”), yet, whereas Amos 5:2 paints a picture of Israel falling and neither getting up nor having someone to lift her up, Psalm 145:14 says that God supports those who fall, and raises up the bowed down.
How could the rabbis have repudiated Amos 5:2, which was God’s word? Did they believe that God had changed his mind about permanently casting down Israel? Did they see Amos 5:2 as hyperbole, yet they believed that David was excluding it from Psalm 145 to avoid giving the impression that Israel’s downfall was permanent, and to avoid spoiling the positive, upbeat Psalm of praise that is Psalm 145?