Subjugation of animal soul gives Hamshacha to Mitzvah:[1]
Angels are not obligated and are not able to fulfill Mitzvos. The reason for this is because they do not have an evil inclination. It is the animal soul of a Jew which makes Mitzvos have the power of drawing down G-dliness. The explanation is as follows: Mitzvos involve matters in the physical world. For a Mitzvah to draw down G-dliness towards these physical items it needs to be prefaced with a subjugation of the animal soul. The subjugation of the animal soul [Iskafya] refines and elevates the Kelipas Noga, and elicits the Hamshacha of G-dliness above which is drawn into the Mitzvos. Since angels don’t have an animal soul which they can subjugate, they are unable to draw G-dliness into the Mitzvos.
[1] Torah Or Toldos 18a