In this matter itself (concerning the union of ‘Mashpia’ and ‘Mekabel’ that takes place during the performance of a Mitzvah) the primary aspect is still the physical act of the Mitzvah. A good example of this is the union of ‘Mashpia’ and ‘Mekabel’ as it is manifested in the actions of the Patriarchs with regards to the ‘Shiduch’ between Yitzchok and Rivkah.
This is so because regarding the ‘Shiduch’ between Yitzchok and Rivkah the purpose here is as the Possuk states: וָאַרְבֶּה אֶּת זַרְעוֹ וָאֶּתֶּן לוֹ אֶּת יִצְחָק “I multiplied his seed, and gave him Yitzchok” and the Possuk states: כִי בְיִצְחָק יִקָרֵא לְךָ זָרַע “In Yitzchok will be called your seed” which refers to Yaakov who was born from Yitzchok and from him, the whole of the nation of Yisroel was born. Regarding this matter the actual birth came through Rivkah who is the ‘Mekabel’. Simply put, with regard to the father, he can make all the preparations and he can have a very good understanding; he can envisage exactly how the births will be but the actual giving birth can only be done by the mother who is Rivkah.
This issue can also be applied to the way things are spiritually. As RaShi says “Avrohom would convert the men, and Soroh would convert the women” and the same was true for Yitzchok and Rivkah but there is an added virtue in Rivka’s achievement.
