davids

I agree it is the heart .Zechariah was looking for a sign as proof from God. Though Zechariah was a Priest in the temple and performed his duties as a Priest; you would expect a Priest to be close to the Lord' but his response was one of doubt and and questioning in disbelief. On the other hand Mary's response was one of faith and trust. Mary knew that even though it was humanly impossible to conceive this way, nothing is impossible for God. And as we read on in verse 38 her response WAS of faith and trust in saying: "I am the Lord's servant; may it be to me as you have said".