冰炭不言，冷热自明 (冰炭不言，冷熱自明) bīng tàn bù yán, lěng rè zì míng

bīng tàn bù yán, lěng rè zì míng phrase ice or coals, whether hot or cold goes without saying; sincerity is not expressed in words
Domain: Proverb 谚语
Notes: (CC-CEDICT '冰炭不言，冷熱自明')