The Lord had established His unconditional covenant with Abram in Genesis 12:2-3, “And I will make of thee a great nation, and I will bless thee, and make thy name great; and thou shalt be a blessing: And I will bless them that bless thee, and curse him that curseth thee: and in thee shall all families of the earth be blessed.” The three main tenants of the Abrahamic Covenant were:

1. The Promised Land of Canaan (Genesis 12:1, Genesis 15:7).

2. The Promise of Numerous Offspring (Genesis 15:4-6, 17:6-8).

3. The Promise of Blessings unto the World (Genesis 12:3).

So much more could be said about the Lord’s covenant with Abraham but let us focus on the question before us.

In Genesis 17:15-17, the Lord tells Abram (whose name is now changed to Abraham – verse 5) that his wife Sarai (whose name has now been changed to Sarah) shall bear him a son.  Genesis 17:15-17 says, “And God said unto Abraham, As for Sarai thy wife, thou shalt not call her name Sarai, but Sarah shall her name be. And I will bless her, and give thee a son also of her: yea, I will bless her, and she shall be a mother of nations; kings of people shall be of her. 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?”  Could this possibly happen to a couple who were 100 years old and 90 years old? 

Abraham knew he would be the father of a great nation (Genesis 12:2), but he perhaps did not think that Sarah would be the one to bare him a son.  In verse 18, Abraham replied to the Lord, “O that Ishmael might live before thee!”  Ishmael was Abraham’s son through Hagar, Sarah’s handmaiden.  (Read Genesis 16:1-11).  Abraham suggested that Ishmael would be the one to inherit God’s covenant blessings.  In verse 19, the Lord spoke again of Sarah bearing him a son, “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.”  It may seem that Abraham’s laugh was one of skepticism and unbelief, but we read in Romans 4:18-21, “Who against hope believed in hope, that he might become the father of many nations; according to that which was spoken, So shall thy seed be. And being not weak in faith, he considered not his own body now dead, when he was about an hundred years old, neither yet the deadness of Sara’s womb: He staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God; And being fully persuaded that, what he had promised, he was able also to perform.”  Abraham’s amazement by the Lord’s words did not take away his faith in the Lord’s words. 

Let us move on to Sarah’s reaction to the wonderful news.  We read in Genesis 18:9-12, “And they said unto him, Where is Sarah thy wife? And he said, Behold, in the tent. And he said, I will certainly return unto thee according to the time of life; and, lo, Sarah thy wife shall have a son. And Sarah heard it in the tent door, which was behind him. Now Abraham and Sarah were old and well stricken in age; and it ceased to be with Sarah after the manner of women. Therefore SARAH LAUGHED WITHIN HERSELF, saying, After I am waxed old shall I have pleasure, my lord being old also?”  Sarah was not thinking of the Lord’s ability to do the impossible, she was thinking of the logical consequences and limitations of her advanced age.  She was momentarily caught up in doubt.  The Lord responded with the rhetorical question, “Is any thing too hard for the LORD? At the time appointed I will return unto thee, according to the time of life, and Sarah shall have a son.” (Verse 14).  So, in love, the Lord reaffirmed His promise and told her she would indeed bear a son to Abraham.

I would be remiss if I ended this meditation here.  Later, in the book of Hebrews the faith of Abraham and Sarah is mentioned, showing us they were both people of great faith, even if in Sarah there was some temporary doubt.  Hebrews 11:8-11 says, “By faith Abraham, when he was called to go out into a place which he should after receive for an inheritance, obeyed; and he went out, not knowing whither he went. By faith he sojourned in the land of promise, as in a strange country, dwelling in tabernacles with Isaac and Jacob, the heirs with him of the same promise: For he looked for a city which hath foundations, whose builder and maker is God. Through faith also Sara herself received strength to conceive seed, and was delivered of a child when she was past age, because she judged him faithful who had promised.”  (461.2)