Rom 4:20 Yet he did not waver through unbelief regarding the promise of God, but was strengthened in his faith and gave glory to God,
With respect to the promise of God, Abraham did not waver in unbelief. He did not vacillate between faith and doubt as many believers frequently do. When from the human viewpoint things are going well, it is easy to trust God. But when things seem impossible, it is even easier to distrust Him.
It would seem from the Genesis narratives that Paul was mistaken about Abraham's unwavering faith. When "the word of the Lord came to Abram in a vision, saying, 'Do not fear, Abram, I am a shield to you; your reward shall be very great,'...Abram said, 'O Lord God, what wilt Thou give me, since I am childless, and the heir of my house is Eliezer of Damascus?...Since Thou hast given no offspring to me, one born in my house is my heir'" (Gen 15:1-3). Abraham openly admitted before God that he could not understand how the divine promise of an heir, much less of a multitude of nations, could be fulfilled. The only heir he could see was his chief servant, Eliezer, who would have received Abraham's inheritance had no son been born to him by Sarah.
But struggling faith is not doubt, just as temptation to sin is not itself sin. The very fact that Abraham was trying to understand how God's promise could be fulfilled indicates he was looking for a way of fulfillment, although he could not yet see a way. Weaker faith might have simply succumbed to doubt. Sincere struggling with spiritual problems comes from strong, godly faith. Such faith refuses to doubt and trusts in God's promises, even when no way of fulfillment is humanly imaginable. God's testing of His children's faith is designed to strengthen their trust, and they should thank Him for it, hard as it seems to be at the time (see James 1:2-4).
2 Consider it pure joy, my brothers, whenever you face trials of many kinds, 3 because you know that the testing of your faith develops perseverance. 4 Perseverance must finish its work so that you may be mature and complete, not lacking anything.
When Abraham was tested by God, he grew strong in faith.
(from The MacArthur New Testament Commentary, (c) Moody Press and John MacArthur, Jr., 1983-2002)
This really touched my heart this morning as it relates to our waiting to see if God will bless us with another child. Sometimes I feel like Abraham, not understanding how it could happen, and I begin to wonder if I am doubting. This study this morning gave me some peace-knowing that trying to understand God's plan for us is not doubt, but simply our faith struggling, exercising our spiritual muscles. And we hope that God is glorified. We want God to have glory no matter when or if he blesses us with another child. He is God, wonderful and awesome, no matter what his plan is for our family. He deserves to be glorified and we are striving to do that daily.
I love it when I study God's words and he reveals things to me that I needed at that time. May anyone who reads this have that same blessing from the Word in your own personal study.