"Behold, I give unto you power1 to tread on serpents and scorpions, and over all the power2 of the enemy: and nothing shall by any means hurt you." (Luke 10:19, KJV)
Luke 10:19 in the KJV mentions "power" twice. Different Greek words are used for the two. The first "power" is a translation of "εξουσιαν (exousian)", often translated as "authority" (28 times in the KJV). The second "power" is a translation of "δυναμιν (dunamin)", often translated as "[physical] power". It has been alleged that the KJV mistranslates "εξουσια" and that translating it as "power" obscures the distinction between it and "δυναμις".
First, it is not an error to translate "εξουσια" as "power" because "power" does mean "authority". The United States Constitution refers to "Powers of Congress", "Judicial Powers", "Powers of the States and People", which describes the authority given to each of those entities.
Second, "power" is a more appropriate word to translate "εξουσιαν" at Luke 10:19. Greek words, as with English words, have a range of meanings and scopes of meanings. In some contexts, "εξουσια" is best translated as "authority". However, the "εξουσιαν" which Jesus gives at Luke 10:19 appears to mean more than just authority. This "εξουσιαν" is that which enables the disciples to "tread on serpents and scorpions, and over all the power of the enemy" that "nothing shall by any means hurt" them. This is authority "with teeth" or authority with enforcement powers. Having authority alone will not enable one to tread upon such dangerous animals. The owner of a plot of land infested with serpents and scorpions certainly has the "authority" to tread upon them, but does he have the "power" or the ability to do so? How great is our God who not only gives us authority but also the power to carry out his will. As "εξουσια" carries this enforcement aspect of authority, one of its definitions is "2) physical and mental power: 2a) the ability or strength with which one is endued, which he either possesses or exercises" (Thayer's Greek Definitions).
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