What did Israel's request to send spies reveal about their faith?
It revealed a weak, unbelieving faith. Although God promised to drive out their enemies and give them the land, they did not trust His word and wanted men to search out the land and confirm it. Their request showed they were taking matters out of God's hands and placing them in human hands.
Les explains that Israel's request to send spies was not God's idea but the weakness of the flesh. God had already told them He would have everything ready, drive out their enemies, and all they would have to do is occupy. Instead, Israel said they did not know and asked to send spies. God in His goodness and graciousness permitted it, though it was not His intention. They said they would send men before them to search out the land and bring back word. Les points out this showed they did not really believe God would do what He said He would do; they wanted men to confirm it and tell them what to do. By asking for spies, they took matters out of God's hands and put them into the hands of mere mortals.
And ye came near unto me every one of you, and said, We will send men before us, and they shall search us out the land, and bring us word again by what way we must go up, and into what cities we shall come.