Adam Clarke on Ecclesiastes 11:1

Cast thy bread upon the waters - An allusion to the sowing of rice; which was sown upon muddy ground, or ground covered with water, and trodden in by the feet of cattle: it thus took root, and grew, and was found after many days in a plentiful harvest. Give alms to the poor, and it will be as seed sown in good ground. God will cause thee afterwards to receive it with abundant increase. The Targum understands it of giving bread to poor sailors. The Vulgate and my old Bible have the same idea. Send thi brede upon men passing waters.