《太平广记·卷三十六·神仙三十六》
这时候众仙人已经回来了。其中有人互相说： 让他不要开北门，他却如此糊涂！可见仙界是不可随便来的。 
其中相谓曰： 令其勿犯北门，竟尔自惑，信知仙界不可妄至也。
Meanwhile, all the immortals had returned. Some of them said to one another, "We told him not to open the north gate, but he had to be so careless! One must know that it's not a good idea to come to the fairyland casually."