What is the difference between unbelief, and just being honest with the Lord? In the first chapter of Luke we find Zechariah rebuked by Gabriel because he didn’t believe the Lord’s message that his wife would have a son in her old age. We also find Mary commended as someone who believed the Lord’s message that she would have a child, even though she was a virgin.
When you look at their responses, they don’t look very different. Zechariah said, "How can I be sure of this? I am an old man and my wife is well along in years.” (v.18). Mary said, "How will this be,” Mary asked the angel, “since I am a virgin?” Even though they ask similar questions, there is obviously a difference in their hearts towards the Lord and His Word.
The Lord is gracious with those who have sincere questions. Think about Abraham when the Lord told him that He was going to judge Sodom and Gomorrah. Abraham was very humble and respectful towards the Lord (like Mary v.38), but it didn’t keep him from asking the Lord honest questions from his heart "Will not the Judge of all the earth do right?" (Gen 18.25).
The Lord engaged with Abraham’s respectful honesty, and I believe He is pleased when we do the same.
Psalms 33:6 (NLT)
The Lord merely spoke, and the heavens were created. He breathed the word, and all the stars were born.