Aaron ben Moses ben Asher (Hebrew: אַהֲרוֹן בֶּן משֶׁה בֶּן אָשֵׁר, romanized: ʾAhăron ben Moše ben ʾĀšēr; 10th century, died c. 960) was a sofer (Jewish scribe) who lived in Tiberias. He perfected the Tiberian system of writing vowel sounds in Hebrew. The system is still in use today, serving as the basis for grammatical analysis.
The Leningrad Codex (Latin: Codex Leningradensis [Leningrad Book]; Hebrew: כתב יד לנינגרד) is the oldest known complete manuscript of the Hebrew Bible in Hebrew, using the Masoretic Text and Tiberian vocalization. According to its colophon, it was made in Cairo in AD 1008 (or possibly 1009).
Some have proposed that the Leningrad Codex was corrected against the Aleppo Codex, a slightly earlier manuscript that was partially lost in the 20th century. However, Paul E. Kahle argues that the Leningrad manuscript was more likely based on other, lost manuscripts by the ben Asher family. The Aleppo Codex is several decades older, but parts of it have been missing since the 1947 anti-Jewish riots in Aleppo, making the Leningrad Codex the oldest complete codex of the Tiberian mesorah that has survived intact to this day.