Psalm 151

Psalm 151 is the name given to a short psalm that is found in most copies of the Septuagint but not in the Masoretic Text of the Hebrew Bible. The title given to this psalm in the Septuagint indicates that it is , and no number is affixed to it: "This Psalm is ascribed to David and is outside the number. When he slew Goliath in single combat". It is also included in some manuscripts of the Peshitta.

The Eastern Orthodox Church as well as the Coptic Orthodox Church, Armenian Apostolic Church and the Armenian Catholic Church accept Psalm 151 as canonical. Roman Catholics, Protestants, and most Jews consider it apocryphal. However, it is found in an appendix in some Catholic Bibles, such as certain editions of the Latin Vulgate, as well as in some ecumenical translations, such as the New Revised Standard Version.

Although for many years scholars believed that Psalm 151 might have been an original Greek composition and that “there is no evidence that Psalm 151 ever existed in Hebrew”, it is now known from the Dead Sea scrolls that this psalm did in fact exist in Hebrew and was a part of the psalter used by the Qumran community.

...
Wikipedia