Cheng Yi (chéng yí 程颐) was a Chinese philosopher born in Luoyang during the Song Dynasty. He worked with his older brother Cheng Hao (chéng hào 程灏).
On a heavy snowy day, there was a young man named Yangshi went to visit his teacher Cheng Yi. He found his teacher was sleeping when he arrived at the house. So he waited in the snow because he didn't want to wake his teacher up. When his teacher finally got up and the snow was very thick. Since then people use this idiom to say some one respect his teacher.
程颢(1032-1085)、程颐(1033-1107)兄弟，均为北宋时期著名理学家和教育家。杨时和游酢去拜会当时著名的理学家程颐。程颐正在闭目养神，杨时、游酢二人恭敬地站在一旁，等了很长时间。程颐醒来，门外已雪深一尺。后人就以“程门立雪”作为尊师重道的范例。“程门立雪”也可说成“立雪程门”。
典故出自于《宋史·杨时传》
