Literally: gold – section – jewel – clause/article (of a document)
Alternately: A golden rule. (Not necessarily The Golden Rule, though.) An important, even foundational principle, for someone’s behavior and life.
Notes: This yojijukugo uses repetition for emphasis: both 金 and 玉 refer to “something of high value,” while 科 and 条 indicate “rules.”
It comes to us from an old acquaintance, the Wen Xuan aka Selections of Refined Literature (Japanese 『文選』 = Monzen) – a 2500+ year old anthology of Chinese poetry and literature.