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.
The verse means: “Show hospitality, even though the corresponding return of hospitality to you may seem improbable; nevertheless, be hospitable in faith.” Compare Luke 14:13-14; Hebrews 13:2. Some interpreters (not unreasonably) understand by “bread” the seed from the produce of which bread is made. Seed cast upon the fertile soil flooded by the early rains would be returned to the sower in autumn with large increase.