Satan was tempting Jesus to take a shortcut rather than to follow God's plan for reaching people. The devil was also leaving some of the scripture out because the scripture says that all who trust in God have nothing to fear, even in dangerous circumstances. Satan failed to mention that a person must first follow God's will. He said only a certain part of the psalm. Todays scriputures are often misquoted and taken out of context.
History is full of examples of cults and sects which used only part of the bible.
Knowing scripture is a vital part of the struggle against Satan. We can then recognize when others use scripture incorrectly. In that verse the children of Israel are instructed to refrain from telling God what to do. Again, the devil took him to a very high mountain and showed him all the kingdoms of the world and their splendor. Most people would be tempted by the thought of gaining the whole world.