“And Zacharias said unto the angel, Whereby shall I know this? for I am an old man, and my wife well stricken in years.”
King James Version (KJV)
1:18 Zacharias said, Whereby shall I know this? - In how different a spirit did he blessed virgin say, How shall this be? Zacharias disbelieved the fact: Mary had no doubt of the thing; but only inquired concerning the manner of it.
Lu 1:18 By what shall I know this? He wanted a sign.