God's abundant grace and unfailing love should influence how people respond to him (see Deuteronomy 30:1–5). After all God had done for the remnant, it was shameful they were so quick to betray him.
grace in the sight of the kings of Persia: Babylon and Assyria had tortured and exiled their enemies (2 Kings 17; 25), but Persia treated exiled people kindly and returned them to their homelands (see Ezra 1:1–3).
a wall of protection: This phrase refers to God's presence protecting the nation of Judah, not the physical walls of Jerusalem, which Nehemiah rebuilt several years later.