What Are You Laughing At? Or Holding On To?

"And without becoming weak in faith he contemplated his own body, now as good as dead, since he was about a hundred years old, and the deadness of Sarah's womb; yet, with respect to the promise of God, he did not waver in unbelief, but grew strong in faith, giving glory to God, and being fully assured that what He had promised, He was able also to perform." (Romans 4:19-21)
v 22..."it was reckoned to him as righteousness."

Somewhere between Abraham's 75th and 86th year, God told him his descendants would be as numerous as the stars in the heavens. He was 86 when Ishmael was born. Sarah had instigated the circumstances leading to Ishmael's birth. Did Abraham think at the time that this would be the fulfillment of God's promise? Maybe. When he was 99, God appeared to Abraham again, explaining the covenant He was making with him and his descendants. And He reiterated that the son to be born from Sarah would be the heir to the promise.
Abraham contemplated his own body and his wife's. Romans 4 affirms Abraham's unwavering faith. He didn't doubt God's promise of blessing and multiplication. But in Genesis 17:18 Abraham said to God, "Oh, that Ishmael might live before Thee!" He had a son already. Rather than give up on what he had possibly figured was the prescription for fulfillment of God's promise, he cried out for God to bless what Abraham had already brought about...by his own effort, at the instruction of his desperate wife.
God assured Abraham He would bless Ishmael, but He had another plan in mind for fulfilling His promise. Isaac. "He laughs." A constant reminder of how unlikely and impossible his parents thought this child's existence was.
Abraham never doubted that God would do what He promised, Paul wrote to the Romans. But it's evident in Genesis that he had preconceived notions about how God might do it. And for a moment at least, he held on to what he thought was best. He wanted Ishmael to be the one, hardly grasping at that moment the significance of what the Lord was about to do.
And so it is with us. There is nothing wrong with sizing up the situation, for if our faith is unwavering, we're just making more room for the Lord to do the extraordinary (Gen 18:14), thereby giving Him glory. Yet even in holding fast to a promise in faith, we may carry an idea of how we think God will bring the fulfillment of the promise to pass. But it's so often not what we think, and we usually have to let go of the answer we have helped to create to make room for the miracle that is about to be birthed.