塞翁失马 (塞翁失馬) sāi wēng shī mǎ

sāi wēng shī mǎ set phrase the old man lost his horse, but it all turned out for the best; a blessing in disguise
Domain: Idiom 成语
Notes: (CC-CEDICT '塞翁失馬')

Also contained in

塞翁失马安知非福塞翁失马焉知非福