The number 123 has no well-established symbolic meaning in biblical tradition, but appears among other things as Aaron's age and in censuses.
123 is not a number attributed special symbolism in the Bible or in Jewish numerology (gematria) in any prominent way. The number nevertheless appears in several biblical contexts. In Numbers 33:39, Aaron's age is given as 123 years when he died on Mount Hor, making this the most notable biblical occurrence of the number. Additionally, the number is mentioned in the censuses in Ezra 2:21 and Nehemiah 7:32, where descendants from Bethlehem and men from Bethel and Ai are counted as 123 respectively. Psalm 123 speaks about lifting one's eyes toward God and asking for grace in humility, but the number itself carries no recognized symbolic meaning beyond these occurrences. Aaron died on Mount Hor after God had commanded Moses to bring him up there. His high priestly garments were transferred to his son Eleazar, marking an important transition in Israel's priesthood (Num 20:25–28). In some modern approaches, 123 is broken down into the components 1, 2, and 3, which individually can symbolize God's unity, testimony or partnership, and divine completeness. However, this is a more recent interpretation without foundation in traditional biblical or rabbinic exegesis. Psalm 123 is one of the fifteen "Songs of Ascents" (Shir HaMa'alot, Ps 120–134) that were traditionally sung by pilgrims on their way up to the temple in Jerusalem.*