According to the Hebrew Bible, Methuselah (Hebrew: מְתֿוּשֶלַח / מְתֿוּשָלַח, Mətušélaḥ / Mətušálaḥ Məṯûšélaḥ / Məṯûšālaḥ ; "Man of the dart/spear", or alternatively "his death shall bring") was the oldest person to ever live. Extra-biblical tradition maintains that he died on the 11th of Cheshvan of the year 1656 (Anno Mundi, after Creation), at the age of 969, seven days before the beginning of the Great Flood. According to the medieval rabbi, Rashi, God delayed the Flood specifically because of the seven days of mourning in honor of the righteous Methuselah. Methuselah was the son of Enoch and the grandfather of Noah.
The name Methuselah, or the phrase "old as Methuselah", is commonly used to refer to any living thing reaching great age.
Read more about Methuselah: Methuselah in The Bible, Extra-Biblical Mentions, Interpretations, Use of The Word in Modern Life