This idiom is: people's hearts are like mirrors, and eyes are like mirrors.
The heart is like a mirror:
Origin: Song Hongmai's Yijian Bingzhi.
Original text: It is also said that the human heart is like a mirror, which must be kept in mind and kept from being contaminated by dust. It is naturally smart.
Definition: The human heart is as transparent and clear as a mirror.
Look like a mirror:
Origin: Partridge Sky by Zou Yinglong of Song Dynasty.
Original text: Turn your spirit when your birthday comes. Look like a mirror and walk like a cloud. Every year, the seniors serve the banquet in the Huatang Hall, and their children will come and go.
Definition: Eyes are bright like mirrors.