Where is the inyan to make the kos overflowwing- kiddush, havdala? Both?
Is there any such inyan by Arba Kosos?
The idea is that the blessing and bounty of Shabbos should overflow into the week. One source is the Gemara (Eiruvin 65) which states that wine that “spills like water” implies blessing for a home. This is only customary for the havdalah cup, and not for the kiddush cup, or for arba kosos.