Romans 9:21

21.Has not the worker of the clay? etc. The reason why what is formed ought not to contend with its former, is, that the former does nothing but what he has a right to do. By the word power, he means not that the maker has strength to do according to his will, but that this privilege rightly and justly belongs to him. For he intends not to claim for God any arbitrary power but what ought to be justly ascribed to him.

And further, bear this in mind, — that as the potter takes away nothing from the clay, whatever form he may give it; so God takes away nothing from man, in whatever condition he may create him. Only this is to be remembered, that God is deprived of a portion of his honor, except such an authority over men be conceded to him as to constitute him the arbitrator of life and death. (306)

“The words, ‘I will have mercy on whom I will have mercy,’ imply that all deserved wrath; so that the lump of clay in the hands of the potter must refer to men already existing in God’s foreknowledge as fallen creatures.” — [Scott ]

In all the instances in which this metaphor is used by Isaiah and Jeremiah, it is applied to the Jews in their state of degeneracy, and very pointedly in Isaiah 64:8 : where it is preceded, in Isaiah 64:6, by that remarkable passage, “We are all as an unclean thing,” etc. The clay then, or the mass, is the mass of mankind as corrupted and depraved. — Ed.