Scripture teaches that God does not change his mind, but he sometimes adjusts his answers to fit our response. The Bible contains many examples of this: the Hebrews on the outskirts of Canaan (see Nu 14:11–23; 1Sa 15:29); Hezekiah’s repentance on behalf of Israel (see 2Ch 29:3–10,36) and the sparing of Nineveh (see Jnh 3:1–10).
Experiencing God’s will is dynamic. As with any interpersonal relationship, God’s relationship with humanity involves unexpected twists and turns. God modifies his responses to ours; we adjust our responses to God’s. So, in a sense, it can be said that God sometimes changes his mind in response to our prayers.
At the same time, God’s will is determined. There are decrees and promises he has made that do not change. He kept his covenant with the Israelites (see Dt 7:7–8) and keeps his new covenant with those who believe in Jesus (see Jn 6:37–40, 44).
These aspects of God’s will work together. It is not possible for us to understand exactly how they work together, but God is ultimately in control. We might compare the relationship between God, his will and his people to a chess match between a novice player and a master. The novice can make any move he chooses and the master will respond accordingly. But the master will always be in control of the game. This analogy is limited and should not be pressed too far, but God’s people “win” when the Master’s will is done.