'Grain' in the Bible

“You will come to your grave in old age,Like the stacking of grain [on the threshing floor] in its season.

“They are exalted for a little while, and then they are gone;Moreover, they are brought low and like everything [they are] gathered up and taken out of the way;Even like the heads of grain they are cut off.

“Will you have faith and depend on him to return your grainAnd gather it from your threshing floor?