Wind and thunder strengthening each other: a hexagram of gain flowing down from those above, favoring bold undertakings and steady self-correction.
Xun ☴, wind, whose quality is entering, stands above Zhen ☳, thunder, whose quality is movement, and Zhu Xi notes that both trigrams also carry the image of wood. He reads the figure as the upper trigram giving its bottom line down to the lower one: those above adding to those below, which is what makes it gain. With the fifth and second lines both central and correct, the text favors going forward, even across the great river.
Judgment (卦辭)
The text attached to the whole hexagram, read when no line is changing.
益，利有攸往，利涉大川。
Yi: it is favorable to have somewhere to go. It is favorable to cross the great river.
The movement runs opposite to that of Hexagram 41, Sun. In Zhu Xi's account, the upper trigram gives up its bottom yang line, which comes down to the very bottom of the lower trigram. Those above are giving to those below, and that is what counts as gain. The fifth and second lines are both central and correct, and both trigrams carry the image of wood, which he links to the crossing of the great river. So the text favors setting out, even over deep water.
Image (大象)
The Image commentary (象傳) reads the whole hexagram from its two trigrams.
風雷，益。君子以見善則遷，有過則改。
Wind and thunder: Gaining. The noble person goes over to the good as soon as he sees it, and corrects his faults whenever he has them.
Wind and thunder each make the other stronger. Zhu Xi sees the same partnership in the noble person's two habits, going over to the good on sight and correcting what is wrong. He calls them the greatest gains a person can make, and says they feed each other in just the same way.
Lines (爻辭)
From the bottom line to the top. In the line names, nine (九) marks a yang line and six (六) a yin line.
Line 1, yang (初九)changing line in the shared reading
利用為大作，元吉，无咎。
It is favorable to use this for a great undertaking. Only with great good fortune is there no blame.
The first line (初九) is the yang line that came down from above, and it receives the most. Zhu Xi says it cannot simply take and give nothing back, so it should put what it has received into some great work. The order of the words matters to him: only if the result is greatly good is it free of blame. A gift raises the standard of what is owed.
Line 2, yin (六二)changing line in the shared reading
或益之十朋之龜，弗克違，永貞吉。王用享于帝，吉。
Someone adds to it a tortoise worth ten pairs, and it cannot be refused. Lasting correctness and firmness bring good fortune. The king makes an offering to the Lord on High: good fortune.
This is nearly the picture of the fifth line of Hexagram 41, Sun: a figure open at the center receives a gift too generous to refuse. Zhu Xi marks the difference. The second line (六二) is a yin line in a yin place, all softness, so the text adds a call for lasting steadfastness. Because it sits low and receives from above, he also reads it as a favorable sign for divining about the great suburban sacrifice (郊).
Line 3, yin (六三)changing line in the shared reading
益之用凶事，无咎。有孚中行，告公用圭。
Increase comes to it through dire events: no blame. With sincerity and walking the middle course, report to the duke, presenting a jade tablet.
Weak, off center and out of place, the third line (六三) has not earned any gain. Yet it stands at the top of the receiving trigram, and Zhu Xi says its gain takes the form of trouble: warnings and shocks are what benefit it. Taken that way, there is no blame. The text then asks for sincerity and a middle course, and the jade tablet, he explains, is how trust was conveyed.
Line 4, yin (六四)changing line in the shared reading
中行，告公從，利用為依遷國。
Walking the middle course, report to the duke, and he follows. It is favorable to serve as the support when the capital is moved.
Like the third line, the fourth (六四) is off center and is reminded to walk the middle course. Zhu Xi reads it as someone set on benefiting those below, who reports to the duke and is heeded. On moving a capital, he quotes an old account: when Zhou moved east, it relied on Jin and Zheng. A capital moved for the people's sake needs support to stand, and he reads the line as favorable for such a move.
Line 5, yang (九五)changing line in the shared reading
有孚惠心，勿問元吉。有孚惠我德。
There is sincerity, and a kind heart. No need to ask: great good fortune. There is sincerity, and kindness comes back to one's virtue.
The fifth line (九五) is the giver at the top, strong, central and correct. Zhu Xi's note traces a circle: when those above treat those below with sincere kindness, those below answer with sincerity and kindness in return. Good fortune of this kind needs no inquiry; it is plain without asking. The phrase fits giving that is not waiting to be repaid.
Top line, yang (上九)changing line in the shared reading
莫益之，或擊之，立心勿恆，凶。
No one adds to it; someone may strike it. Setting the heart without constancy brings misfortune.
At the top line (上九), a yang line at the far end of gain keeps reaching for more. That, Zhu Xi says, is why no one adds to it and someone may even strike at it. He treats the phrase about a heart without constancy as a warning, not a sentence already passed. Gain that never stops wanting turns into its opposite.
If you drew this hexagram
Which text to read depends on how many lines are changing. With none, read the judgment; with one, read that line; with more, follow Zhu Xi's rules in the Yixue qimeng.
Text: Zhu Xi, Yuanben Zhouyi benyi (原本周易本義), Siku Quanshu Wenyuange copy, as transcribed by the Kanseki Repository (KR1a0031), corrected and punctuated by K-magpie. Translation and explanation: written by AI (Claude) from Zhu Xi's commentary and checked against the text and commentary. Sources and the list of corrections are on the Today's Hexagram page.
Characters corrected in this hexagram — Line 1, yang (初九): 大作无吉 → 大作元吉 · 怕 → 恆 (transcription)