萧史，是春秋时代秦穆公时期的人。
他擅长吹箫，他的箫声能吸引许多美丽的孔雀和白鹤来到庭院中。
秦穆公有一个可爱的女儿名叫弄玉，她非常擅长吹笙。
因此，她希望嫁给一个精通音乐的人。
后来，秦穆公找到了萧史。
他发现萧史不仅气度不凡，风度翩翩，而且吹箫的技艺非常高超。
于是，秦穆公对萧史非常满意，并决定把女儿弄玉嫁给他为妻。
婚后，萧史开始教弄玉吹箫。
他教她如何吹出美妙的凤鸣声。
经过数年的努力，弄玉终于能够吹出像凤凰一样动听的声音了。
她的箫声甚至能够吸引天上的凤凰飞来，停在他们的屋顶上。
秦穆公看到这一切后，感到非常高兴。
为了庆祝他们，他还特地为他们建造了一座叫做“凤台”的建筑。
从此以后，萧史和弄玉就住在这座凤台上，不再需要吃喝，也没有下来过。
有一天，夫妻俩人在月光下吹箫。
突然，一条金龙从凤台右边飞来，一只彩凤从左边飞来。
于是，萧史骑上了金龙，弄玉坐上了彩凤，两人一起腾空而起，飞向天空。
这就是成语“乘龙快婿”的由来。
因为萧史是乘坐着龙升天的，而且他是秦穆公非常喜爱的好女婿，所以这句成语常用来称赞别人的女婿。
它寓意着一个令人满意的、非常优秀的女婿。
Xiao Shi was a man during the Spring and Autumn period of the State of Qin.
He was skilled in playing the flute, and his music could attract many beautiful peacocks and white cranes to gather in the courtyard.
The King of Qin had a lovely daughter named Nong Yu, who was very good at playing the sheng.
Therefore, she hoped to marry a man who was proficient in music.
Later, the King of Qin found Xiao Shi.
He discovered that Xiao Shi was not only noble and elegant, but also an excellent flutist.
Thus, the King of Qin was very satisfied with Xiao Shi and decided to marry his daughter Nong Yu to him.
After marriage, Xiao Shi began to teach Nong Yu how to play the flute.
He taught her how to produce a beautiful phoenix sound.
After several years of hard work, Nong Yu finally managed to make sounds as beautiful as a phoenix.
Her flute music could even attract celestial phoenixes to fly down and perch on their roof.
Seeing all this, the King of Qin felt very happy.
To celebrate them, he specially built a building called 'Phoenix Terrace' for them.
From then on, Xiao Shi and Nong Yu lived on this Phoenix Terrace without needing food or drink, never coming down again.
One day, the couple played the flute under the moonlight.
Suddenly, a golden dragon flew in from the right side of the terrace, and a colorful phoenix flew in from the left side.
Then, Xiao Shi rode on the golden dragon, and Nong Yu sat on the colorful phoenix. The two of them rose into the sky together.
This is the origin of the idiom 'Dragon-Riding Son-in-Law'.
Because Xiao Shi ascended to the heavens on a dragon and was a beloved son-in-law of the King of Qin, this idiom is often used to praise someone's son-in-law.
It implies a satisfactory and outstanding son-in-law.
