The fourth line of Revolution (King Wen 49) is drawn as yang, the numeral nine in the old divination manuals. James Legge's translation renders the line as occasion for repentance disappearing, if he is believed in even while changing existing ordinances, there will be good fortune. The image sits inside a hexagram whose judgment as a whole concerns believed in only once it is accomplished, great progress and success, advantage in being firm and correct, so that any occasion for repentance disappears, and this line supplies one stage of that larger reading rather than a complete statement on its own.
Structurally the line stands at the lowest place of the upper trigram Dui, lake in Legge's readings of the eight trigrams, while the lower trigram of the hexagram is Li, fire in the same traditional set of images. The Great Symbolism of the hexagram reads fire in the midst of the waters of a marsh; the superior man regulates his calendar and makes clear the seasons and times, and the fourth line takes its place inside that combined picture of Li below and Dui above.
Read on its own the line neither opens nor closes the hexagram's argument. It marks the point where Dui is either forming (in the lower trigram) or completing itself (in the upper), and later interpreters treat its image, Changing Existing Ordinances, as the concrete case through which the hexagram's abstract judgment becomes visible in a single situation rather than a general principle.