Hexagram 27 is the twenty-seventh hexagram of the I Ching, with the upper trigram Gen (Mountain) and the lower trigram Zhen (Thunder). The mountain rests above, thunder stirs below — evoking the image of a mouth: the upper and lower jaws with movement between them. This is the hexagram of nourishment in all its forms: what we take in through the mouth (food and drink), what we express through it (words), and more broadly, how we nourish body, mind, and spirit.
The character "Yi" depicts a jaw and chin, representing the mouth and the act of nourishing. The hexagram's image — mountain above, thunder below — shows stillness containing movement, like jaws chewing. The two yang lines (First Nine and Nine at the Top) form the lips, while the four yin lines between them represent the empty mouth, ready to receive.
The Judgment: Perseverance brings good fortune. Pay heed to the providing of nourishment and to what a person seeks to fill his own mouth with.
The Judgment instructs us to observe carefully: what do we nourish ourselves with, and what do we nourish others with? Physical food sustains the body; words and ideas nourish the mind; virtue and wisdom nourish the spirit. A person's character is revealed by what they choose to take in and give out. "Perseverance brings good fortune" — only sustained, principled nourishment leads to lasting well-being.
The Image: At the foot of the mountain, thunder. Thus the superior person is careful of his words and temperate in eating and drinking.
The mountain stands still while thunder moves below — the superior person emulates this by exercising restraint in speech (the mountain's stillness) while being mindful of nourishment (the thunder's vitality). Being "careful of words" means speaking only what is true and beneficial; being "temperate in eating" means taking in only what truly nourishes.