i.e. When the congregation understood by the relation of Moses and Eleazar, and by other signs. So seeing is used Genesis 42:1 Acts 7:12. Thirty days; the time of public and solemn mourning for great persons. See Deuteronomy 34:8.
Related Commentaries of Numbers 20:29
Numbers 20:29
29 And when all the congregation saw that Aaron was dead, they mourned for Aaron thirty days, even all the house of Israel.