During the Tang Dynasty, a scholar named Wei Gu from Duling, orphaned as a child, was eager to marry and start a family. He asked matchmakers everywhere to find him a wife, but no matter how hard he tried, he could never find the right match.
In 807 AD, during the Tang Dynasty, a man named Wei Gu was traveling to Qinghe when he stopped in Songcheng and lodged at an inn south of the city. A fellow guest offered to arrange a marriage for him with a daughter of the Pan family from Qinghe, instructing Wei Gu to meet him before dawn the next day at the gate of Longxing Temple, west of the inn, to hear the reply.
Eager to secure this prestigious match, Wei Gu set out early while the moon still hung bright in the sky. At the temple steps, he spotted an old man leaning against a cloth sack, flipping through a ledger by moonlight. Curious, Wei Gu approached and saw that the characters in the book were utterly unrecognizable. Puzzled, he asked, "Old sir, what book is this? I've studied hard since childhood and even know Sanskrit, but I've never seen these script before."
The old man smiled and said, "These are books from the underworld. How could you recognize them?" Wei Gu was greatly startled and said, "Then you must be a person from the underworld. What do you do there?" The old man replied, "I am an official of the underworld, in charge of marriage matters across the world."
Wei Gu was overjoyed and quickly said, "I've been wanting to start a family, but things never worked out. Now someone has invited me here to discuss an engagement with the Pan family—I wonder if it will succeed?"
The old man shook his head and said, "It will not succeed. Your wife is only three years old now and will not enter your home until she is seventeen." Wei Gu noticed a cloth pouch by his side and asked, "What is in that cloth pouch?"
The old man replied, "They are all red cords, used to bind the feet of husband and wife. From the moment they are born, I secretly tie their feet together with these red strings. No matter if they are enemies, rich or poor, noble or lowly, or separated by vast distances—once this string is tied, they are destined to become husband and wife. Your foot is already bound to hers; what use is there in seeking another match?"
Wei Gu asked again, "Where is my wife? What does her family do?" The old man replied, "North of this inn, there is an old woman named Chen who sells vegetables. Her daughter is your wife. Chen often carries her daughter while selling vegetables. I can point her out to you."
As dawn broke, Wei Gu's awaited person never arrived, so he followed the old man to the market. There, a ragged, one-eyed old woman carried a three-year-old girl, shouting to sell vegetables. The old man pointed at the girl and said, "She is your future wife."
With that, the old man vanished into thin air.
Wei Gu was furious and shouted, "You old demon, how dare you toy with me! I come from a respectable scholar-official family—how could I be matched with a blind old woman's ugly daughter!"
After returning to his inn, Wei Gu ordered his servant to kill the little girl, promising a heavy reward for the deed. The servant took a knife, stabbed the girl between the eyebrows, and fled. The marketplace erupted in chaos as people chased the assassin, but Wei Gu and his servant managed to escape.
Years later, Wei Gu, now an official, finally married a beautiful 17-year-old girl, but was puzzled by the flower ornament she always wore between her brows. When he asked why, she replied, "When I was three, my nurse carried me through the city, and a madman stabbed me here, leaving a scar I've hidden ever since."
"I was originally born into an official family, but after all my family members died, I was fostered by my wet nurse, Granny Chen. At age three, Granny Chen took me to the market to sell vegetables, where a bandit stabbed me, leaving a scar between my eyebrows, so I wear a flower patch to cover it. Later, my uncle became an official, and I followed him, marrying off as his daughter."
Wei Gu was startled and said, "That was the one I sent someone to stab!"
Wei Gu then recounted the entire story to his wife, from beginning to end. Only then did they realize that the old man under the moon had long ago tied the red thread around their feet. From that day forward, they cherished and respected each other even more deeply.
Later, the idiom "Old Man Under the Moon" came to refer to the god in charge of marriage or to be used as a synonym for matchmaker.
Source: *Xu Xuan Guai Lu*, Chapter "Ding Hun Dian"
Meaning of the Idiom: Later, the Chinese idiom "月下老人" came to describe how the god in charge of marriage or a synonym for matchmaker is referred to.