Here again Abraham doubts God. Maybe by the time his generation is alive, people were having babies before ninety, but his ancestors were hundreds before and/or still having children. This is the second time Abraham directly questioned God. He also indirectly questioned him by laying with his maid.
God continues to keep his covenant with Abraham although he questions God's timing. God must have favor on Abraham to allow the covenant to continue. Just as God still continues to love us even when we turn our back to him. He still wants us to come back, no matter what we have done. We are his children.
Dear Lord, though we question your timing with our lives and things that go on in our lives, please continue to keep your Covenant with us. Thank you for not turning your back on us when we don't believe. Please keep calling us back to you. Amen.