I'm having a difficult time trying to find languages that have a phonemic contrast between /ʂ/ and /ʃ/.
I can hear the difference without difficulty because /ʂ/ sounds like a lower frequency range of noise than /ʃ/ does.
Polish [...] contrast[s] denti-alveolar [s, z, ts, dz], alveolo-palatal [ɕ, ʑ, tɕ, dʑ], and retroflex [ʂ, ʐ, tʂ, dʐ] places of articulation. In addition, a palatalized palatoalveolar sound [ʃʲ] exists as an allophone of /ȿ/ when this phoneme occurs before [i] or [j] as in To[ʃʲ]iba ‘Toshiba’.
In "Typology of the Syllable-Initial Consonants in the Chinese Dialects" by Wai-Sum Lee, I found /ʂ/ and /ʐ/ in more than one variety of Chinese fricatives, but not /ʃ/.
Are there languages that phonemically contrast /ʂ/ and /ʃ/?