den Ast absägen, auf dem man sitzt

Literally, "to saw off the branch on which one is sitting".

den Ast absägen, auf dem man sitzt

1. (idiomatic) to undermine one's own position; to act in a way that will eventually make one lose something that one is dependent on

• This idiom is often used to convey the meaning of English to bite the hand that feeds you. However, the German saying is broader as it is not specific to causing harm to a benefactor. There is also the literal equivalent in die Hand beißen, die einen füttert, though this is somewhat less common.