By faith Abraham, even though he was past age—and Sarah herself was barren—was enabled to become a father because he considered him faithful who had made the promise. And so from this one man, and he as good as dead, came descendants as numerous as the stars in the sky and as countless as the sand on the seashore. Hebrews 11:11-12
It would be very easy for me to pass right over these verses and justify it by saying that not a lot of people are actually reading these devotions. You see, these scriptures are painful to read because my wife and I aren't able to have children and raise them here on earth. They're even more painful when others have quoted the verses back to us as evidence that our faith is lacking or any number of comments made by well-meaning people. As I'm learning, not every promise given to men and women in the Bible is for me or you (for instance, God told Abraham he'd be the father of many nations, not any of us). But I've chosen to go through the Hall of Faith, and this particular miracle deserves a word or two.
We all know the story. Both Abram and Sarai were in their 80s. God told Abram his heirs would outnumber the stars in the sky. Sarah convinced Abram to sleep with her maid, and Ishmael was the result. When Abram and Sarai were in their 90s, God again told Abram (now Abraham) that he would be the father of many nations and that Sarai (now Sarah) would be the mother to bear that child. Sarai overheard it and laughed. Isaac was the resulting child.
If you've ever uttered the words, "okay, but I'm not sure how you're going to do it" then you understand faith a little. It wasn't Abraham or Sarah's "problem" to circumvent the laws of biology to produce Isaac. That was God's "problem." It was Abraham and Sarah's responsibility to care for the child when he was born. After doubting a little (through their laugh), they believed.
The takeaway for this passage is this: "Abram believed the LORD, and he credited it to him as righteousness" Hebrews 15:6. It's the fundamental truth of our faith.