Adam Clarke on Nehemiah 6:18

He was the son-in-law of Shechaniah - Previously to the coming of Nehemiah, the Jews seemed to be fast intermixing with the heathen, by intermarriages with Ashdodites, Ammonites, and Moabites; see Neh 13:23. Ezra had many evils of this kind to redress, (Ezr 9:3, etc.), chiefly among the common people, though there were both chiefs and priests in that trespass. But here we find the heathen and Jewish nobles interlinked; and the latter were so far imbued with the spirit of idolatry, that they forgot God, his service, their brethren, and their own souls.