冰冻三尺，非一日之寒 (冰凍三尺，非一日之寒) bīngdòng sān chǐ, fēi yī rì zhī hán

bīngdòng sān chǐ, fēi yī rì zhī hán phrase three feet of ice does not form in a single day; Rome wasn't built in a day
Domain: Proverb 谚语
Notes: (CC-CEDICT '冰凍三尺，非一日之寒')