Luke 1:18 - Clarke's commentary and critical notes on the Bible

And Zacharias said unto the angel, Whereby shall I know this? for I am an old man, and my wife well stricken in years. Whereby shall I know this? - All things are possible to God: no natural impediment can have any power when God has declared he will accomplish his purpose. He has a right to be believed on his own word alone; and it is impious, when we are convinced that it is his word, to demand a sign or pledge for its fulfillment.