《北史·列传·卷七》
如果永远居留北方，没有好的文化作为主导，你们的子弟们也免不了面墙而立，一无所见吧！ 
若永居恆北，遇不好文主，卿等子弟不免面墙也。 
If you stay in the north forever, without a good culture as a guide, your children will not be able to avoid standing against the wall and seeing nothing!