青,取之于蓝,而青于蓝;冰,水为之,而寒于水。
Blue dye comes from the indigo plant yet is bluer than indigo; ice is made from water yet colder than water.
Plain meaningA student or successor can surpass the teacher.
Original context and translation note
English wording on Gu Ren Said is an original reading aid, not a claim that there is only one valid literary translation.