Luke 1:18 Commentary - Whedon's Commentary on the Old and New Testaments

18. Whereby shall I know? This bold putting the angel to the proof was a want of proper faith. The fact that the angelic visitant knew his prayer, the splendour of his person, and the tremor of Zacharias, were vouchers sufficient. Strauss notes that Zacharias’s Greek words here are precisely the same with the Greek words of Abraham, according to the Septuagint in Gen 15:8, and asks why Abraham was gratified and Zacharias punished. Grotius had answered Strauss’s question centuries before it was asked. Abraham had been instructed by no previous example; Zacharias was instructed by the example of Abraham, which as a priest he was bound to understand. But Zacharias’s penalty, like his fault, was slight. It was discipline rather than punishment. And Grotius, literal as is his spirit, finds in the dumbness and beckoning of Zacharias a type of the then existing silence of prophecy, leaving the nation to the premonitions of the rites and ceremonies alone until the Messiah be born.