1. The children of Zion (Isaiah 49:20-21) are addressed. Their servitude is not irrevocable; Jehovah has not formally repudiated Zion (Deuteronomy 24:1); nor, though they had to learn by discipline, can any creditors claim His people as slaves (2 Kings 4:1): cp. Jeremiah 24:4-6; Ezekiel 37.
2, 3. The imagery is from the exodus from Egypt.