What does Luke 4:12 mean?

Satan has been tempting Jesus in a moment of hunger and loneliness (Luke 4:1–8). These enticements vary, but all center on Jesus stepping away from God's will in favor of something easier, quicker, or more comfortable. Christ resisted all such attempts. He submitted to God the Father and cited Scripture. In one of the temptations, the Devil himself quoted the Bible, twisting the words and their context (Luke 4:9–11). His suggestion was for Jesus to jump off the highest point of the temple, claiming that God had promised to keep Him safe no matter what He did.

Once again, Jesus quotes from the Old Testament book of Deuteronomy. This reference closely follows the passage Jesus cited when refusing to worship Satan (Luke 4:8; Deuteronomy 6:13). The words are Moses' reminder that God's people ought not "put [Him] to the test" (Deuteronomy 6:16). Moses refers to an incident where Israel essentially "dared" God to let them die of thirst, rather than trust Him to provide for their needs (Exodus 17:1–7).

Had Jesus jumped, God would likely have spared Him, just as God provided for the stubborn Israelites. However, that act would have short-circuited the plan for mankind's salvation (Matthew 16:21). Jesus doesn't doubt that God would keep Him safe; rather, He trusts God the Father enough not to attempt to force His hand.