路遥知马力，日久见人心日（事）lù yáo zhī mǎ lì,rì jiǔ jiàn rén xīn

遥：遥远。路途远了，可以知道马的力气大小，时间长了可以看出人心的好坏。as distance tests a horse’s strength,so time reveals a person’s heart; as a long road tests a horse’s strength, so a long task proves a person’s heart