Genesis 11:19

And Peleg lived after he begat Reu two hundred and nine years, and begat sons and daughters.

Genesis 11:19 belongs to the genealogical record in Genesis 11 and records that Peleg lived 209 years after he begot Reu. That record shows human longevity declining after the Flood, with Peleg's 209 years after Reu's birth far less and far fewer years than the years lived by the generations from Adam to Noah before the Flood. The patriarchs after the Flood lived shorter lives than the patriarchs from Adam to Noah, and the average length of life had been decreasing. As one link in the genealogy from Shem to Abraham, the 209 years Peleg lived after begetting Reu helps leave Shem alive 150 years after the birth of Abraham and 50 years after the birth of Isaac. In this way the knowledge God taught Adam could be given directly from Adam to Methuselah to Shem to Abraham and Isaac to Jacob the father of the tribes of Israel.