Dec 7

Luke 1: 18-25

Zechariah asked the angel, “How can I be sure of this? I am an old man and my wife is well along in years.”
The angel said to him, “I am Gabriel. I stand in the presence of God, and I have been sent to speak to you and to tell you this good news. And now you will be silent and not able to speak until the day this happens, because you did not believe my words, which will come true at their appointed time.”
Meanwhile, the people were waiting for Zechariah and wondering why he stayed so long in the temple. When he came out, he could not speak to them. They realized he had seen a vision in the temple, for he kept making signs to them but remained unable to speak.
When his time of service was completed, he returned home. After this his wife Elizabeth became pregnant and for five months remained in seclusion. “The Lord has done this for me,” she said. “In these days he has shown his favour and taken away my disgrace among the people.” 

Having been terrified that he was about to be killed just a moment ago, Zachariah is now challenging the message the angel has brought him.  You can almost imagine the angel gaping at him in open mouthed surprise.  
I know that I have prayed for something to happen and when it has, I have been a bit taken aback.  Are you sure God?  This? But the answer has never been delivered to me via angel mail.  I hope I would be a little less challenging in that situation!
I think that Zachariah wasn't doubting that God had the power to give them a baby, but just didn't believe it could happen.  He feels he is too old.  I do laugh that he doesn't say Elizabeth is old, but just "getting along in years".  Tact and diplomacy, that man!
Because Zachariah doubted God and showed a lack of faith, he was punished.  He wasn't allowed to speak until the baby was born.
The people in the temple must have all been wondering what was going on - they might have thought that Zachariah had met his end in the temple, but then he came out. They recognised that something big had happened when he was unable to speak. And he managed to convey what had happened in the temple. I find it interesting that he still had to finish his "turn" as priest in the temple before going home.
Elizabeth conceived and then went into seclusion for 5 months. I wonder why - I would have thought she would be out there showing off her baby bump and happy to be able to put the gossipers in their places.  Maybe she had a really bad first trimester.
What I learn from this part of the nativity scene - never underestimate God's power and believe that He will answer your prayers.