Isaiah 56:3 - Ellicott's Commentary On The Whole Bible

Neither let the son of the stranger... — Two classes of persons were likely to suffer specially from Manasseh’s policy — (1) the heathen proselytes, who, as in Psalms 87, had been admitted as citizens of Zion under Hezekiah’s special protection; and (2) in the highest degree, those of that body who had been taken, as Ebed-Melech afterwards was (Jeremiah 38:7), into the king’s household as eunuchs. The courtiers of Manasseh would taunt them as aliens, and in the second case would press the letter of Deuteronomy 23:2. The principle of Isaiah’s teaching was, of course, applicable to the Israelites who, like Daniel and his friends, had been mutilated against their will by heathen conquerors (Daniel 1:3), and most commentators refer the words to such cases. It is scarcely probable, however, that the household of Hezekiah would have been supplied with home-born eunuchs, and, on the hypothesis which I have adopted, I find in the eunuchs a sub-section of the proselytes. The words put into the mouths of the complainers are the natural utterances of men treated as they had been.