“Because of faith also Sarah herself received physical power to conceive a child, even when she was long past the age for it, because she considered God Who had given her the promise to be reliable, trustworthy and true to His word.” Hebrews 11:11
Now this is encouraging to me that Sarah is included in the Hall of Faith, because she did not have faith initially. God told Abraham he would have an heir and be a mighty nation, when this did not happen right away Sarah thought maybe it was not through her. Wow, does that sound familiar. First, that something doesn’t happen right away and second, we start to try and arrange things.
The good news is that even though Sarah told Abraham to take her servant, Hagar, to have a child to be the heir, God still used Sarah. That tells me that even though I make mistakes and step out of God’s will He will still use me. Abraham and Sarah were told again that they would have a child, even in their old age, they believed by faith and it happened.