If we study the lifespans of the Biblical figures from the Flood and on, they declined from 950 (Noah) to 600 (Shem) to the 400’s, and then to the 200’s.Then going from Abraham to Moses, they went from the upper 100’s to the middle and lower, down to 120 with Moses.See also Ha’amek Davar who observes dryly that by then a person’s human faculties have virtually left him.
In fact, there were many people in the Torah who lived much longer than 120. There are two possible sources for that expression. Before the Flood, when God first saw mankind sliding to evil ways, He stated: “My spirit will not contend regarding man forever since he is but flesh. Some of the commentators understand this to mean God had placed a new upper limit on man’s lifespan.
God recognized that man was sinful because the antediluvian lifespan was so great.
Why, Moses’s own brother Aaron lived till 123, and our forefathers down to his time lived well upwards of 120.
In modern times, Jeanne Calment beat the limit by over 2 years.
"If something extremely bad occurs, people forget all their usual daily worries and become totally preoccupied with this single, truly serious problem.
For example, your worry about your brother's serious illness is pre-eminent and has displaced all other worries, because they all pale in comparison.
(In fact, Noah was commanded to begin construction of the ark a full 120 years in advance (and on top of a mountain) so that people would notice and inquire – and perhaps Noah’s response would stir them to repent in time.) A second possible source is Moses’s lifespan.
Moses lived till exactly 120 (Talmud Sotah 13b) – and on top of it the Torah attests that his energy and vitality did not diminish in the slightest before that time (Deut. We thus bless people today that they be granted the same long, productive life of our great teacher Moses.
See likewise Pirkei Avot (), which is even less forgiving: “At Ninety to be bent over; at one hundred it is as if the person has died and passed and is ‘nullified’ from the world.” Based on this, it is definitely possible a person could live a bit longer than 120.
But either way, it's a pretty good blessing to wish someone!
In the second half of the 16th century, Jews were subject to grave Church-sponsored persecutions: Pope Julius III and Pope Clement VIII condemned the Talmud and other Hebrew writings as "obscene," "blasphemous" and "abominable" -- and ordered them all seized and burned.