"Zacharias said to the angel, “How will I know this for certain? For I am an old man and my wife is advanced in years.”
The angel Gabriel, bearing good news, showed up at the altar while Zacharias performed his priestly duties. I'm guessing that Zacharias knew that God had opened Sara's womb to conceive Isaac in her old age. So isn't it interesting that Zacharias would doubt Gabriel's pronouncement that Elizabeth in her advanced years would conceive John? Zacharias wanted to know how he could be certain this wonderful thing would happen, and Gabriel responded by telling him that because he doubted Zacharias would be mute until John's birth. And so he was. It's easy to judge Zacharias for his unbelief, but don't we often do the same thing when we doubt God's promises? We know how faithful He has been in the past, yet our circumstances seem so impossible that we can't bring ourselves to trust Him to do what He says He will do. At such times we need to spend time recounting God's past faithfulness, then ask Him to give us certain faith as we wait on Him.