מדרש אויף דברים 27:3

"And you shall write them": I might think (that he could write them) on stones — you, therefore, reason: It is stated here "writing," and, elsewhere (Ibid. 24:1) "writing." Just as there, on a scroll, here, too, on a scroll. You reason this way; but I can also reason: It is stated here "writing," and, elsewhere (Ibid. 27:8) "writing." Just as there, on stones, here, too, on stones! — Would you say this? There is a difference. I can learn one thing from another, and I can deduce one thing from another. I can learn one thing that obtains for all generations from another than obtains for all generations; but we do not deduce a thing that obtains for all generations (i.e., our instance) from something that obtains only for that time (i.e., the instance of the stones). As it is written (Jeremiah 36:18) "And Baruch said to them: From his mouth he read all these words to me, and I wrote it in the book with ink."