This prose line, written as the close of an early collection of David’s prayers, before the final collection of the Psalms, is not part of this psalm (see Hebrew title of Psa 86). It is omitted by some Hebrew manuscripts and the Syriac. Instead of the Hebrew prayers the Septuagint has “songs”; the difference between the two words in Hebrew is of one letter only.

Quoted with permission from Bratcher, Robert G. and Reyburn, William D. A Handbook on the Book of Psalms. (UBS Helps for Translators). New York: UBS, 1991. For this and other handbooks for translators see here .