This belief is commonly held by Christians as well. It comes from Genesis 6:3: “The LORD said, ‘My Spirit will not strive with man forever, because he also is f

This belief is commonly held by Christians as well. It comes from Genesis 6:3: “The LORD said, ‘My Spirit will not strive with man forever, because he also is flesh; so his days will be one hundred twenty years.’” At that point, Genesis had described several individuals as having lifespans in the hundreds of years, most famously Methuselah at 969 years. This is sometime before the Flood. Note that interpreting this verse as a lifespan limit is not universal—an alternative reading (possibly a more popular one) is that 120 years in this context refers to how many years were left until the Flood. After the Flood, Genesis continues to describe individuals with long lifespans, but they decline rapidly. Abraham, for example, died at 175, ten generations after Noah. Later, in the post‐Exodus era, Deuteronomy says that Moses died at age 120.