'Grain' in the Bible

“You will come to the grave in full vigor,Like the stacking of grain in its season.

“He will not become rich, nor will his wealth endure;And his grain will not bend down to the ground.

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

“Will you have faith in him that he will return your grainAnd gather it from your threshing floor?