Gen 17:17 And Abraham fell upon his face and laughed. And he said in his heart, "Can a child be born to a man a hundred years old, or can Sarah bear a child at ninety?"

Gen 18: 11 Now Abraham and Sarah were old, advanced in age; the way of women had ceased to be for Sarah. 12 So Sarah laughed to herself saying, "After I am worn out and my husband is old, shall this pleasure be to me?"

Luke 1:18 And Zechariah said to the angel, "By what will I know this? For I am an old man, and my wife is advanced in years!"

Luke 1:34 And Mary said to the angel, "How will this be, since I have not had sexual relations with a man?"

4 texts that describe the reaction of 4 individuals to a miraculous birth. Observe the following:

1. The promised birth was miraculous - in 3 cases to those past the age of childbearing, and in one v special case not related to the normal process at all!

2. The completely natural reaction to such an impossibility. We can take heart from these examples that doubting the power of God is not just the province of those weak in faith, but even those who are seasoned saints and anointed vessels. We can take comfort in the fact that they were 100% human just like us! It is also very very interesting to note that the very first person to doubt the virgin birth was Mary herself... there you go critics!

3. Our God does not let our doubts, whether genuinely and openly expressed, or privately held ( as in the cases above ) hinder His sovereign determination to bless! Truly there is no shadow of turning with him! It is such a great comfort that He is so much bigger than our mean conception of Him. His promises once made are kept.

So, elect of the Lord, rejoice!! His purpose to save you from the beginning of time will not be thwarted by your weak and stumbling faith or your doubting heart! Do not think your arm of flesh will save you, but rest in the faithfulness of He who has foreknown, predestined, called, justified and will glorify you!
"being confident of this very thing, that He who has begun a good work in you will complete it until the day of Jesus Christ " Phil 1:6