The Rabbis taught in a Baraita that upon entering a barn to measure the new grain one should recite the blessing, "May it be Your will O Lord, our God, that You may send blessing upon the work of our hands." Once one has begun to measure, one should say, "Blessed be the One who sends blessing into this heap." If, however, one first measured the grain and then recited the blessing, then prayer is in vain, because blessing is not to be found in anything that has been already weighed or measured or numbered, but only in a thing hidden from sight.