Isaiah 66:5

The Lord addressed the faithful who did tremble at His Word (Isaiah 66:2). He would put to shame their ritualistic brethren, who hated them for their reality and excluded them for emphasizing genuineness. Those who obeyed God’s Word would find great joy and comfort in that Word.

These two groups of Israelites emerged conspicuously following the return from exile, but they also existed in Isaiah’s day (cf. Isaiah 5:19; Luke 6:22; John 16:2). One group worshipped God for His sake, and the other for their own benefit. The ritualists challenged the "spiritual" to find their joy in the Lord, while not really believing-they themselves-that obedience was the key to that joy. God promised that as they had shamed their spiritually sensitive brethren, so He would shame them in the end.