As you saw the iron mixed with soft clay, so they will mix with one another in marriage, but they will not hold together, just as iron does not mix with clay.
Daniel here gives full satisfaction to Nebuchadnezzar concerning his dream and the interpretation of it. That great prince had been kind to this poor prophet in his maintenance and education; he had been brought up at the king's cost, preferred at court, and the land of his captivity had hereby been made much easier to him than to others of his brethren.
Commenting on Daniel 2:31-45
And whereas thou sawest iron mixed with miry clay,.... That is, iron among the clay; otherwise iron and clay will not mix and cement together, as is affirmed in the latter part of the verse; but as some of these toes were of iron, and others of clay, or some part of them were iron, and some part of them of clay, they shall mingle...
And whereas thou sawest iron mixed with miry clay, they shall mingle themselves with the seed of men: but they shall not cleave one to another, even as iron is not mixed with clay. (y) They will be marriages and affinities think to make themselves strong: yet they will never by united in heart.