What the text says. In seven short verses David speaks in the first person: he was the youngest of his brothers and kept his father’s sheep; his hands made a musical instrument; the Lord sent his angel and anointed him; his tall brothers were passed over; he went out against the Philistine and cut off his head with the giant’s own sword. Its title in the Greek calls it David’s own psalm, but “outside the number,” that is, standing beyond the 150.
Where it is found. The psalm stands in most manuscripts of the Septuagint and in some Syriac and Latin traditions, but not in the Masoretic text (Very Strong). For a long time scholars thought it had been written in Greek. Then the great Psalms Scroll from Qumran Cave 11 (11Q5), found in 1956 and published by James A. Sanders, proved to contain two Hebrew psalms, usually called 151A and 151B, which lie behind the Greek. The Greek psalm combines and shortens them (Strong).
What the Orthodox Church reads. The Orthodox Church accepts Psalm 151 and prints it at the end of the Psalter, though it is not one of the psalms read in the regular weekly cycle. It is a fitting close: the Psalter that began with the blessed man ends with the shepherd boy whom God chose and anointed, a shepherd-king in whom Christians see a figure of Christ, the Son of David.
How other traditions handle it. The Catholic Church does not count Psalm 151 as canonical, though it appears in some Vulgate editions and in some ecumenical Bibles. Protestant Bibles and the Jewish Scriptures do not include it. The Oriental Orthodox Churches also accept it.
What it does and does not change. Psalm 151 adds no new doctrine. It retells, as prayer, what 1 Samuel 16–17 narrates. Its discovery in Hebrew at Qumran is a good example of how the Septuagint often preserves real Hebrew traditions rather than inventing new ones.