Matthew Poole and continuators on Jeremiah 35:7

7 Neither shall ye build house, nor sowe seed, nor plant vineyard, nor have any: but all your days ye shall dwell in tents, that ye may live many dayes in the land where ye be strangers .

The last words of the verse probably give us a reason of the former, they were no Native Jews, but strangers amongst them, who commonly are envied, when they are observed to thrive too much, or to live splendidly; and that envy of the Natives of the place where they sojourn, exposeth them to their Hatred and Malice, so as their lives are made uneasie to them, Jonadab therefore cautions his Sons to avoid these inconveniencies by a thrifty, sober, laborious life, to which they had been bred, in keeping Flocks, and to avoid any thing might expose them to Envy or Hatred or Malice of the People amongst whom they were come to sojourn.