Washing Out the Cup Before Kiddush, Continued, Continued

I posted a while back about a custom some have to put some water into the cup to be used for kiddush and then pour that water into the wine bottle.

I gave three suggestions: 1) Remove pegam of the wine; 2) dilution as described in the gemara of their thick wine; and 3) the kabbalistic requirement to wash out even a clean cup prior to kiddush, followed by a need to put the water somewhere. I prefer #3, out of all of these.

My father told me that Rabbi Friedman does the same thing, and SoccerDad told me he saw it at Rabbi Rosenberg's table. They both give the same reason: The red wine represents din, judgment, and we add water to be mamtik (sweeten) then din with chesed (water). I still consider #3 to be somewhat plausible, with a practice of specifically putting the water into the wine bottle afterwards, once the water was in the glass, to be coming from this reason of being mamtik the din, or else with this reason developing afterwards and then reinforcing the custom.

Update: A bit later, Rabbi Rosenberg emailed me something else he came across on this subject, from the Raavya:

ראבי"ה ח"ב - מסכת ראש השנה סימן תקמז

ומה שאנו מטילין מים בכוס של הבדלה ושותים ומה שנשתייר אנו רוחצין פנינו, כדי לחבב את המצות, ואמרו חכמים שיורי מצוה מעכבין את הפרענות

And this that we pour water in the cup of havdalah and drink (presumably the water itself), and from what is left over we wash our face, is in order to make the precepts dear, and the Sages said that the remnants of the precepts hold back the punishment.

This seems to be specifically the cup of havdalah, and it is not before drinking the havdalah wine but rather when cleaning it out afterwards. Thus, there is mostly water in the cup and a bit of wine stickiness. Yet we hold these remnants dear and drink the water, and use it to wash our face.

This custom may indeed be related to this other custom of pouring water to clean out the cup for kiddush, then pouring that into the wine bottle such that, here too, we can drink this water. If so, when at someone else's house, they might appreciate it if you poured the water into your hands and used it to wash your face, or into a separate cup to drink later, rather than pouring it into the bottle.