Halakhah su Geremia 32:78

And Rambam, may his memory be blessed, wrote (Mishneh Torah, Laws of Testimony 3:4) that the main testimony of the Torah is from the mouth of witnesses and not from the mouth of their writing, as it is stated (Deuteronomy 17:6), "By the mouth, etc."; except that because of the betterment of the world, such that people would find [those from whom] to borrow, the Sages ordained that we establish law with regard to money according to witnesses in a deed, the same as from their mouth. But Ramban, may his memory be blessed, (in the Sefer HaMitzvot at the end of the second root) challenged him greatly about this in the Sefer HaMitzvot. And if I would come to write the whole matter, it would be lengthy. But the essence of the thing is that Ramban, may his memory be blessed, holds that the testimony of a deed is from Torah writ, as it is written (Jeremiah 32:44), "write in the book, and seal."