Job 5:5- The hungry consume his harvest, taking it even from among the thorns, and the thirsty pant after his wealth.

There are two possible explanations for this saying.

First, it may refer to a thief which steals ALL the grain, even that which is growing among thorns.

Or-

There is an ancient Middle Eastern custom of farmers, after they have threshed out the grain, hiding it in the chaff or some other private place near the floor and then covering the pile with thorns to keep it from being stolen or eaten by animals. Robbers who found and took this would literally be taking it from among the thorns.