originality of Shakespeare's Witches, which has been well answered
by Mr. Lamb in his notes to the Specimens of Early Dramatic Poetry:

"Though some resemblance may be traced between the charms in Macbeth
and the incantations in this play (the Witch of Middleton), which is
supposed to have preceded it, this coincidence will not detract much
from the originality of Shakespeare. His Witches are distinguished
from the Witches of Middleton by essential differences. These are
creatures to whom man or woman plotting some dire mischief might
resort for occasional consultation. Those originate deeds of blood,
and begin bad impulses to men. From the moment that their eyes first
meet with Macbeth's, he is spellbound. That meeting sways his
destiny. He can never break the fascination. These Witches can hurt
the body; those have power over the soul.--Hecate in Middleton has a
son, a low buffoon: the hags of Shakespeare have neither child of
their own, nor seem to be descended from any parent. They are foul
anomalies, of whom we know not whence they are sprung, nor whether
they have beginning or ending. As they are without human passions,
so they seem to be without human relations. They come with thunder
and lightning, and vanish to airy music. This is all we know of
them.--Except Hecate, they have no names, which heightens their
mysteriousness. The names, and some of the properties which
Middleton has given to his hags, excite smiles. The Weird Sisters
are serious things. Their presence cannot co-exist with mirth. But,
in a lesser degree, the Witches of Middleton are fine creations.
Their power too is, in some measure, over the mind. They raise jars,
jealousies, strifes, 'LIKE A THICK SCURF O'ER LIFE.'