John Oswalt's commentary on Isaiah is great! Here are two brilliant comments; read and digest carefully:
On Isaiah 5:20-21
Alas for those who say of evil good and of good evil,
setting darkness for light and light for darkness,
setting bitterness for sweetness and sweetness for bitterness.
Alas for those who are wise in their own eyes, and discerning in their own sight.
[translation by Oswalt]
If the ethical imperative is dependent upon human reason alone, that reason is no match for rampant self-interest. In fact, self-interest will press reason into service to justify its own behaviour. Only a prior commitment to the revealed wisdom of God... and a commitment to call good good, despite the reasonings of the wise of this world, can make possible genuine long-lasting righteousness both in individuals and in society. The path of those who chart their own course leads inexorably from self-aggrandizement to the ultimate reversal of moral values.
On Isaiah 8:14-15
For the Lord can be a sanctuary and he can be a stone for tripping over and a rock for stumbling upon for the two houses of Israel; a snare and a trap for the inhabitants of Jerusalem.
Many among them will stumble; they will fall abd be crushed, become ensnared and taken captive.
[translation by Oswalt]
The attitude we take toward God will determine what aspect of him we will experience. To those who sanctify him, who give him a place of importance in their lives, who seek to allow his character to be duplicated in them, he becomes a sanctuary, a place of refuge and peace. But to those who will not give him such a place in their lives, he becomes a stone to trip over. He does not change; only our attitude determines how we experience him. Those who make a place for him discover that he has in fact made a place for them. They know that what happens to them comes from One who is both all-powerful and good. In that certainty they can accept and apply whatever comes to them with equanimity and confidence. Those who will not make a place for him will keep colliding with him and tripping over him, for he is there, whether they acknowledge him or not. Because he is a fact of which their hypothesis does not take account, their experiment will keep failing and he will be the cause of it, not because of some vindictive streak in him, but simply because he is and they are trying to live as if he were not. As the New Testament makes plain, it is in Jesus that the double-edged nature of God's self-revelation because most pointed: to those who accept him as God's sufficient sacrifice, he is life and peace; to those who refuse to do so, he becomes a fact over which to stumble again and again (Matt. 21.44; Luke 2:34; Rom 9:33)