The person who performs a mitzvah, who prays or directs his mind toward the Divine, in so doing creates an angel, which is a sort of reaching out on the part of man to the higher worlds.
Such an angel, however, connected in its essence to the man who created it, still lives, on the whole, in a different dimension of being, namely in the world of formation.
And it is in this world of formation that the mitzvah acquires substance.
This is the process by which the specific message or offering to God that is intrinsic in the mitzvah rises upward and introduces changes in the system of the higher worlds-foremost in the world of formation.
From here, in turn, they influence the worlds above them.
So we see that a supreme act is performed when what is done below becomes detached from particular physical place, time, and person and becomes an angel.
–Rabbi Adin Steinsaltz