I Ching hexagram 27
Hexagram 27: Yi
Nourishment · 山雷頤 · Mountain above, Thunder below
Nourishment runs both ways here, in what you take in and in what you provide for others.
What this hexagram is about
What feeds you, and what you feed in turn, is the subject, including the people you look after. Yi (Nourishment) pictures an open mouth, and the image text advises care with speech and moderation with food.
A way to think about it
What have you been feeding lately, including your attention and the people you care about? Would you defend that choice if someone watched it closely?
The text, with Legge's translation
Judgment
貞吉。觀頤，自求口實。
Î indicates that with firm correctness there will be good fortune (in what is denoted by it). We must look at what we are seeking to nourish, and by the exercise of our thoughts seek for the proper aliment.
Steady, correct nourishment is a good sign. The text asks you to look at what a person feeds and at how they provide for themselves, since both show what they value.
Image
山下有雷，頤；君子以慎言語，節飲食。
(The trigram representing) a mountain and under it that for thunder form Î. The superior man, in accordance with this, (enjoins) watchfulness over our words, and the temperate regulation of our eating and drinking.
Line 1 · 初九
舍爾靈龜，觀我朵頤，凶。
The first line, undivided, (seems to be thus addressed), 'You leave your efficacious tortoise, and look at me till your lower jaw hangs down.' There will be evil.
Dropping your own means of sustenance, a spirit tortoise that lives on air, to stare at someone else's meal is the mistake here. Envy of what others have is the bad sign.
Line 2 · 六二
顛頤，拂經，于丘頤，征凶。
The second line, divided, shows one looking downwards for nourishment, which is contrary to what is proper; or seeking it from the height (above), advance towards which will lead to evil.
Looking downward for support turns the usual order upside down, and so does begging from the high hill above. Either way you are looking in the wrong place, and moving ahead goes badly.
Line 3 · 六三
拂頤，貞凶，十年勿用，无攸利。
The third line, divided, shows one acting contrary to the method of nourishing. However firm he may be, there will be evil. For ten years let him not take any action, (for) it will not be in any way advantageous.
You go against the right way of feeding yourself, and sticking with it, even firmly, is a bad sign. For ten years nothing from this path is any use.
Line 4 · 六四
顛頤吉，虎視眈眈，其欲逐逐，无咎。
The fourth line, divided, shows one looking downwards for (the power to) nourish. There will be good fortune. Looking with a tiger's downward unwavering glare, and with his desire that impels him to spring after spring, he will fall into no error.
A person in a high position looks to a capable one below for help, and that is fine here. The tiger-like gaze is steady and intent, and nothing in it can be faulted.
Line 5 · 六五
拂經，居貞吉，不可涉大川。
The fifth line, divided, shows one acting contrary to what is regular and proper; but if he abide in firmness, there will be good fortune. He should not, (however, try to) cross the great stream.
You lean on someone stronger because you cannot supply what is needed yourself, which breaks the usual order. Staying put and steady is the safe course, and a large undertaking is out of reach.
Line 6 · 上九
由頤，厲吉，利涉大川。
The sixth line, undivided, shows him from whom comes the nourishing. His position is perilous, but there will be good fortune. It will be advantageous to cross the great stream.
Everyone depends on you as the source of nourishment. That is a heavy responsibility, and carried with awareness of its risk, it is a good sign and a time to take on something large.
Chinese text: the received Zhouyi, public domain. English: James Legge, The Yi King, Sacred Books of the East vol. 16 (1882), public domain. Plain notes written by this site.
Questions
I cast hexagram 27. Which text do I read?
With no changing lines, read the judgment: "Î indicates that with firm correctness there will be good fortune (in what is denoted by it). We must look at what we are seeking to nourish, and by the exercise of our thoughts seek for the proper aliment." With changing lines, read the lines that changed. When several change at once, Zhu Xi's rules decide which text leads, and the casting page marks it for you.
What are the nuclear, opposite and inverted hexagrams of Yi?
The nuclear hexagram is 2. Kun (Earth). The opposite is 28. Da Guo (Overload). The inverted hexagram is Yi itself, since the figure reads the same upside down.