17 Then Abraham fell upon his face, and laughed, and said in his heart, Shall a child be born unto him that is an hundred years old? and shall Sarah, that is ninety years old, bear?
18 And Abraham said unto God, O that Ishmael might live before thee!
19 And God said, Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac: and I will establish my covenant with him for an everlasting covenant, and with his seed after him.
20 And as for Ishmael, I have heard thee: Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly; twelve princes shall he beget, and I will make him a great nation.
21 But my covenant will I establish with Isaac, which Sarah shall bear unto thee at this set time in the next year.
Abraham was incredulous when God pronounced that he and Sarah would have a child in their old age, and he suggested that God establish His covenants with Ishmael instead. God acknowledges the request, explaining that he has a separate covenant made for Ishmael, but He also stresses that Sarah will indeed bear a son. He even gives a very precise deadline for the event, foretelling that Isaac will be born at this same time one year from now.
Many times we hold out hope for God’s promises, and then feel crushed when we perceive them as being unfulfillable. In our natural lives things expire, what was possible becomes impossible, and that which is not accomplished in the right season won’t be accomplished at all. Abraham had heard before this promise that he and Sarah would have a son, but he had perceived that opportunity as being expired, due to their old age.
But God does not operate under the same constraints as the rest of us. At times it might seem “too late,” or “physically impossible” for Him to fulfill His promises to us. But no matter, He’ll do it anyway!