Adam Clarke on 1 Chronicles 1:20

Joktan begat Almodad - "He divided and measured the earth by lines. Sheleph; he assigned rivers to be boundaries. Hazarmaveth; he prepared a place of snares to kill by the highways. Jerah; he built inns, and when any person came to eat and drink, he gave him deadly poison, and so took his property." - T.

According to these traditions, the two first were geographers; the third, a public robber; and the fourth, an unprincipled innkeeper, who gave poison to his rich guests, that he might get their property. Such things have been done even in modern times.