There is so much more to say on Beshalach, but another week has gone by and been swallowed up by other business, so on to Yisro.
The Rambam describes the mitzvah of kiddush in Sefer haMitzvos 155:
הציווי שנצטווינו לומר דברים ביום השבת בכניסתו וביציאתו
He echoes the same in Mishne Torah (Shabbos 29:1):
מצות עשה מן התורה לקדש יום השבת בדברים
From the Rambam's language it's pretty clear that the mitzvah of kiddush requires "devarim," the recitation of words. It must be done verbally.
Question: The gemara (Meg. 18) tells us that if not for the fact that the Torah uses the double-expression of "zachor" and "lo tishkach" we would assume that the mitzvah of zechiras Amalek could be fulfilled b'lev, mentally, buy just thinking about Amalek. Since no such double-expression is used in connection with the mitzvah of kiddush, it stands to reason that one can fulfill "zachor" of kiddush by thinking alone, through hirhur.
Why does the Rambam say otherwise?