Isaiah 42:10-17 is a declaration by God against the idolatry of the people of Israel, but at the same time it is also a promise that God will keep those who trust Him even in the midst of darkness on the more dense way.
The prophet Isaiah wrote:
15 I will lay waste the mountains and hills
and dry up all their vegetation;
I will turn rivers into islands
and dry up the pools.
God has always hated idolatry, and this is obvious, since God does not share His glory with anyone, and it seems that idolatry was one of the weaknesses of the people of Israel from the beginning. Remember when the people of Israel left Egypt, that Moses went up to speak with God and while He was arriving, Israel erected a golden calf. After this strong event, even such a people in various scenarios of their existence continued to do the same. And here we are once again, in another time and another scenario, and God still has to continue correcting their bad acts.
It is very true that God is very merciful, but it is also true that God pours out His wrath on the children of evil (Romans 1:8). In verse 15 of Isaiah 42 God pronounces judgment against the people of Israel, but not only pronounces judgment but also gives word of encouragement to all those people who trust in Him:
I will lead the blind by ways they have not known,
along unfamiliar paths I will guide them;
I will turn the darkness into light before them
and make the rough places smooth.
These are the things I will do;
I will not forsake them.
Jesus has promised to be with us until the end, He will guard us against evil, will free ourselves from temptation and to make us walk in steadfast places. God will always keep us on the way, since by our own strength we will not be able to stand. Let us give glory to God for His love and mercy.