After the dramatic shift from a focus on the nation as the suffering servant to a focus on the person who will become the suffering servant and the Redeemer, Isaiah continues to develop the identity of the suffering servant, the man who would become the Messiah. Is 54 tells us the Maker is the Husband of His people and the Holy One of Israel is their redeemer.
His great compassion for His people is detailed in Is 55. He is gracious and will deliver His people but they have to do their part in pursuing His righteousness (Is 55:6-9).
We find a huge surprise in Is 56:1-8. Foreigners can partake of God's blessings. The Jews will struggle for centuries over what these verses mean, eventually misinterpreting them as deeming it necessary for anyone wanting a relationship with God to become Jewish. This notion is actually the antithesis of grace which comes freely and is unmerited. God does not require those who come to Him to change before coming to Him. He will take them as they are, then He will transform them.
The blessing to the nations and the redemption of His people will occur regardless of the failing of Israel's leaders (Is 56:9-12) and their ungodly worship of idols (Is 57:1-13). Then it becomes apparent that only those who repent with a contrite heart will be delivered (Is 57:14-16).
Is 58 carries this idea further, indicting those who perform empty religious rituals that are not God-centered. It is not the method of worship, the nationality of birth, the position occupied or the social rank that will save. It is a heart that worships and longs to please God. One that surrenders completely to the suffering Servant, sent by God to redeem His people.