《魏书·列传·卷五十》
语说 担心的是做一件事情的人不一定知道为什么要去做，知道为什么要做的人不一定能够去做 ，为臣实在谈不上知道，不过是勉强为之。
语曰 患为之者不必知，知之者不得为 ，臣诚不知，强欲为之耳。
It is said, "Those who worry about doing something do not necessarily know why it should be done; those who know why something should be done do not necessarily know how to do it." I, your subject, do not presume to know, but I simply do my best.