覆水难收 fùshuǐ-nánshōu

[spilt water can’t be gathered up;what is done cannot be undone;it is hard to get it back again;water poured on the ground cannot be recovered] 倒在地上的水难收回来。比喻事成定局,无法挽回(多用于夫妻离异)

成媒不说,覆水难收。——《敦煌变文集》