Return whence you came.

从那里来，就回到那里去。

There was no reply, whence he inferred that all had gone.

没有回音，因此推想大家都走了。

From whence is it?

这是从哪里来的。

the source from whence it springs

这事发生的根源。

Know neither one's whence nor one's whither.

不知从何处来，也不知往何处去。