"August 23, 1904 Until now, about everything, I taught by word of mouth. But you forget. Because you forget, I have informed you with the tip of My writing brush. The tip of the writing brush may seem light but it is weighty. You must not take it lightly. It is the basis of My teachings. It will not do to misinterpret it. . . . Concerning the truth I have taught you until now, the kana syllabary may feel soft, yet it conveys key teachings. The spoken word is easily forgotten. The written word is unlikely to be forgotten."
January 1, 1970
https://en.wikiquote.org/wiki/Ofudesaki