台Taivo A Taiwan Mandarin dictionary

鑒往知來

jiànwǎngzhīlái

ㄐㄧㄢˋ ㄨㄤˇ ㄓㄌㄞˊ

Simplified 鉴往知来

1to observe the past to foresee the future (idiom, taken loosely from Book of Songs); studying ancient wisdom gives insight into what is to come

Keep 鑒往知來 and it comes back until you know it.