Reference for Berakhot 30:26

אצטריך סד"א נילף כתיבה כתיבה מהתם מה התם אלות אין צואות לא אף הכא נמי צואות לא כתב רחמנא וכתבתם אפי' צואות:

It is necessary [to mention this point] ; because it might have entered thy mind that I mean we can draw an analogy from the use of the verb "to write" in the former instance, thus : As there [with reference to the woman suspected of adultery] the curses were to be written and not the words of the command, so here likewise [with the Tefillin] the words of the command were not to be written! Therefore the All-merciful wrote, "And thou shalt write them" i.e. even the words of the command.

Jastrow