Kedusha Question

Shalom!

Thank you for your question.

The Shulchan Aruch states that “it is proper to have one’s feet together when reciting Kedusha with the chazzan.” This is because Kedusha is the prayer in which we praise G-d in the same manner as the angels do. As such, it is only proper that we should stand with our feet together to imitate them, as legs and feet of angels appear as one. According to other sources, we keep our feet together in order to recall that the Kohanim would walk up the ramp of the altar with their feet together. 

Regaridng until when one must keep one’s feet together: the Elya Rabba insists that the requirement to keep one’s feet together during Kedusha is in effect until having answered amen to ha’El hakadosh the reason being that since we could say that when one responds amen to a blessing, it comes to include everything that was mentioned in the course of the blessing.… In this case, the amen of ha’El hakadosh comes to include the entire Kedusha and it is, in fact, the conclusion of the Kedusha. This is especially true for congregations who have the custom to conclude the Kedusha with l’dor va’dor. 

Nevertheless, le'halcha (Me'ikar Hadin) we rule that one may separate one’s feet after having recited yimloch. According to this approach, the ha’El hakadosh blessing is not truly a component of the Kedusha. 

OC 95:4; 125:2; Mishna Berura 95:8; Terumat Hadeshen 28; Elya Rabba 95:7; Shulchan Aruch Harav 125:2; Aruch Hashulchan, OC 95:5; Kaf Hachaim, OC 125:16;