cast one's bread upon the waters

From the Biblical verse “cast thy bread upon the waters: for thou shalt find it after many days.” (Ecclesiastes 11:1)

cast one's bread upon the waters (third-person singular simple present casts one's bread upon the waters, present participle casting one's bread upon the waters, simple past and past participle cast one's bread upon the waters)

1. (idiomatic) To perform a kind deed or favor without the motivation of any immediate reward or benefit to oneself, though with the possibility of eventual future return.
   • 1930, Dorothy Sayers, Strong Poison:

     “… We shall always feel a melancholy pride, Mr. Grimsby and myself, in knowing that we recognised his quality, before there was any likelihood of financial remuneration. A succès d’estime, that was all, until this very grievous occurrence. But when the work is good, it is not our habit to boggle about monetary returns.”
     ”Ah, well!” said Wimsey, “it sometimes pays to cast your bread upon the waters. …”