不經一事 means “You can't gain knowledge without practical experience.”

This is the short form (first half) of a longer Chinese proverb. These 4 characters remind you that wisdom only comes from experience.

You can translate this 不经一事不长一智 Chinese proverb in a couple of ways.
The first is: You cannot gain knowledge without practice.
The second, and perhaps more popular way is: Wisdom comes from experience.

It literally means if you are inattentive to your affairs or situations you encounter, you will not gain or grow any wisdom or intellect.

It's been said that wisdom comes from good judgment, and good judgment comes from experience, while experience comes from a series of times when you used bad judgment.

經驗是智慧之母 is a Chinese proverb that makes the simplest connection between experience and wisdom.

See Also:  Failure is the Mother of Success | Wisdom | Learn From Wisdom

三人寄れば文殊の知恵 literally means “when three people meet, wisdom is exchanged.”

Some will suggest this means when three people come together, their wisdom is multiplied.

That wisdom part can also be translated as wit, sagacity, intelligence, or Buddhist Prajna (insight leading to enlightenment).

In the middle of this proverb is “monju,” suggesting “transcendent wisdom.” This is where the multiplication of wisdom ideas comes from.

Note: This is very similar to the Chinese proverb, "When 3 people meet, one becomes a teacher."

Note: Because this selection contains some special Japanese Hiragana characters, it should be written by a Japanese calligrapher.