From "Introduction to The Tree of Life" by Baal HaSulam
We find qualitative power in strength, As in lions and leopards Whose quality of power of their strength, Deters all people from fighting them.
Whereas in others We find power and strength Without any quality at all, but Rather quantity alone, Such as in flies.
As a result of their multiplicity No man will fight them. These wanderers walk freely In people's homes And on set tables, And people feel weak Compared to them.
That is not so With other unwanted guests, Such as field flies, insects and the like, Although their force is of greater quality Than that of house flies.
People will not rest or be at ease, Until the last one is driven out. That is because nature Did not endow them With the force of multiplicity, Like flies.