NET
18 Zechariah said to the angel, “How can I be sure of this? For I am an old man, and my wife is old as well.”
Darby
18 And Zacharias said to the angel, How shall I know this, for *I* am an old man, and my wife advanced in years?
KJV
18 And Zacharias said unto the angel, Whereby shall I know this? for I am an old man, and my wife well stricken in years.