The quote which I'm seeking the original German for is:
"lend your ears to music, open your eyes to painting, and . . . stop thinking! Just ask yourself whether the work has enabled you to 'walk about' into a hitherto unknown world. If the answer is yes, what more do you want?"
which Richard Cytowic apparently got from Kandinsky, V. (1910) Über das Geistige in der Kunst. Inbesondere in der Malerei. Munich: Piper.
I've attempted without success to identify the original German here as well as to find something similar in a few English translations like this one with a search of the word music and other relevant words. This appears to be a retranslation from English back into German, rather than the original, but my German isn't very good, so I can't swear to that.