Isaiah 43:2 (ESV) … “When you pass through the waters, I will be with you; and through the rivers, they shall not overwhelm you; when you walk through fire you shall not be burned, and the flame shall not consume you.”
The very events that might cause Judah to question God’s care of them are his doing. He ‘stirred up one from the east’ (41:2) who is now conquering every nation that lies in his path. But this agent is only doing the Lord’s bidding. Judah needs to know that this Lord is the one who bid there be light and there was light. The same Lord will one day bring this world to a close. Nothing, from beginning to end, happens without his ‘say so’ (41:4), which is why his chosen people need not fear. When God chooses someone, that person stays chosen (41:8–10). God doesn’t change his mind, and he doesn’t discard his people. He stays committed to them as their God, and he stays with them. These two things are always true, so they are spoken in the present tense in 41:10a. Then we move to the future tense as the Lord promises that he will strengthen, will help and will uphold. Their enemies shall be confounded and shall be as nothing (41:10–11). The strength that the Lord is going to give will enable a weak worm to move—or actually remove—mountains (41:14–15). His help comes in answer to prayer, in unexpected and impressive ways that bear the hallmark of God’s activity (41:20).[1]
[1] Thomson, A. (2012). Opening Up Isaiah (pp. 116–117). Leominster: Day One.