A source-first reading note for Hexagram 21, Shi He (Biting Through), with a reference translation, trigram frame, and one reversible observation practice.
Reference translation
Biting Through. Success. It is favorable to let justice be administered. The Commentary on the Decision says: When there is something between the jaws, it is called Biting Through. Biting through brings success. The firm and the yielding are divided; movement joins with clarity; thunder and lightning unite and reveal their brilliance. The yielding attains the central place and moves upward. Though it does not stand in its proper position, it is favorable to administer justice. The Image says: Thunder and lightning—Biting Through. Thus the ancient kings made the penalties clear and gave firm order to the laws.
See the original-text and authority layers in the complete catalog entry.
Context from the authority layer
The Tuan commentary on Shi He explains it as "something within the mouth," while the Xiang commentary explains it as "thunder and lightning together." According to the Tuan commentary, "biting" removes the object so that passage is restored. The Zhengyi says: "When something lies in the mouth, it separates upper from lower; if biting removes it, then upper and lower come together and attain 'success.'" The Tuan commentary borrows the image of the mouth to convey meaning, using it as a metaphor for criminal law. Whenever things fail to come together, it is because of obstruction between them; whenever things are uneven, it is because of transgression.
Read the structure before the slogan
The lower trigram is 震 (雷), associated in the bundled corpus with 动; the upper trigram is 离 (火), associated with 丽. Read the lower trigram as the inner or starting field and the upper trigram as the outward field before turning the pattern into advice.
One accountable observation practice
Copy one concrete verb, condition, or image from the reference translation for Hexagram 21. Name one place where it is observable in the situation you are examining. Then choose one small step you can reverse and write the condition that would make you review it.
Common misread to avoid
Do not turn Biting Through into a personality label, a guaranteed event, or a verdict about another person. The translation and trigram frame are source layers to examine, not an instruction to surrender judgment.
Source boundary
The reference translation and context are drawn from Yarrow's bundled structured Zhouyi authority layer. Yarrow keeps that layer separate from optional modern reflection. This page does not claim that Hexagram 21 was cast for your question.