Contrasting Israel with God's Servant.
Israel is responsible for the captivity she is facing- her iniquity. God has the power to deliver, but instead He dried up the seas and clothes the sky in dark sackcloth.
Sometimes there is a dark night of the soul of our own making.
The MacArthur Bible Commentary addresses God's rhetorical questions about the certificate of divorce selling them to His creditors by proposing that He did give the northern tribes of Israel a certificate of divorce and it was permanent. Apparently, when a man divorced his wife, she could remarry, but never remarry that man. Israel went into captivity and was permanently absorbed into Assyria. (Although all of the tribes except Ephraim and Dan are accounted for in the 144,000 in Revelation.) However, the Lord is saying that He did not divorce Judah or permanently sell her. Her punishment is temporary because he has a covenant with David and his descendants.
Comparatively, His Servant listens and learns and obeys, like a disciple.
This suffering Servant exhibits the "upside down kingdom" (as the Bible Project refers to it) but allows the torture and humiliation from the enemy. He can successfully do this because the Lord god helps Him. He is not disgraced and is able to set His face like flint through the ordeal.
He claims His vindication from the Lord and challenges anyone who thinks they have a case against Him.
Behold, the Lord God helps Me; who is he who condemns Me? Behold, they will all wear out like a garment; the moth will eat them.
Isaiah 50: 9
The last two verses are a comparison.
In verse 10, the author points out that if you fear the Lord and obey, in times when you're walking in darkness, you can trust in Him and rely on Him.
But in verse 11, the author those who in time of walking in darkness decide to try make light with your own fire, you will find torment. There's one way to salvation. you cannot write your own ticket. No religion, works, personal belief system, or attitude is a replacement.
Verses 4-11 are the third of the four Servant Songs.