This pericope concludes the section begun at Isaiah 56:1 dealing with the need for humility and holiness in the redeemed people of God. Isaiah explained that the basis of God"s acceptance and blessing of His redeemed people was righteousness ( Isaiah 56:1-8). Then he showed that Israel lacked that righteousness ( Isaiah 56:9 to Isaiah 57:13). Her leadership was wicked ( Isaiah 56:9 to Isaiah 57:2) and her populace was apostate ( Isaiah 57:3-13). Now he explained that the solution to Israel"s predicament was Yahweh"s enablement (grace). The only way she could be what she should be was with the Lord"s help. This section explains how the promise that ended Isaiah 57:13 could possibly come to pass. [source][source][source]
The structure of this section is the opposite of the former one. There, threatening ended with a brief promise, but here, promise ends with a short threat. [source][source][source]