Jesus showed us how to answer Satan's lies in Matthew 4:3-4:
"Now when the tempter came to Him, he said, 'If You are the Son of God, command that these stones become bread.' But He, Jesus, answered and said, 'It is written, "Man shall not live by bread alone, but by every word that proceeds from the mouth of God."'
We live by God's Word. God's Word is there for us to live by—it’s our daily bread, our spiritual food.
Jesus frequently spoke to problems, commanding them to submit to God's will. He cast out demons with words. He commanded sickness to leave. He spoke, "Peace, be still," to the wind and waves during a terrifying storm while on a small boat on the Sea of Galilee (Mark 4:39).
Jesus told us that if we speak to the mountain—whatever it is in our lives that we want removed, as long as it’s not from God—and believe, God will remove it for us (Mark 11:23).
When we declare scripture, we’re speaking to the mountain—the problem that needs to be removed from our lives—and God does it.