So here we have the infamous "laughing" circumstance. Sarah's laugh was one of doubting and distrust. Now immediately following God's pronouncement, she drew attention to her doubt, in verse 12, when she laughed within herself, and said those things we just read. Her laugh was not one of joyful anticipation of such a great blessing, and God, who had His back turned to her, immediately discerned and corrected her, reminding her with His question, "Is anything too hard for the LORD? She then added insult to injury by denying that she laughed a laugh of doubt. She was not only doubting, but now she was fearing as well.
It is indeed a shameful thing to sin in this manner, but she was adding iniquity to iniquity, as it says in another place in the Bible, by covering it up with the lie that she had not laughed. There are a couple of lessons, here, for us.
This startling statement is intended by God to be not merely instruction, but also a fairly strong threat as well. Children can put things over on their parents because, humanly, we lack the powers to be aware of everywhere at all times. But with God, our spiritual Father, there is no such limitation. So consider this. In the narrative of Genesis 18, it gives no indication of any external manifestation of Sarah's doubt. He read her mind without even looking at her.
God's judgment of Sarah was different from the judgment of Zachariah. Other than a verbal correction by Him of her, there was no punishment. Now was God playing favorites? No. There is no partiality with God. I want you to recall though that Zachariah was not merely a righteous man, he was also a priest and, therefore, a leader of the community. God discerned the source of Zachariah's response, and it did not measure up to His standard for Zachariah.
Remember the principle that Christ gave us regarding God's judgment. "To whom much is given, the much more is required." Sarah's reaction was generated by weakness. Her laugh was not a harsh antagonistic scorn, and God immediately discerned this, and He judged accordingly. And though Zachariah was not antagonistic, his skepticism really counted heavily against him. He should have known better.
On the other hand, interpreting laughter is interesting and instructive. Where everyone is honest, open, and free—so is the laughter. If it is just polite, derisive, or carrying innuendo—there is discord (speaking in general terms). Abraham's wife, Sarah, is a prime example of this.
Sarah's relationship with God lacked honesty, trust, and faith at that time—which is revealed in her response to God's promise. Those who clearly speak in controlled tones also raise a question as to why. For example, on a witness stand often you see people trying to control their voices. Is it because they are right? Or because they are afraid of being found out? Well, it could be either; and that is up to us to discern at the moment. The tone of the witness's reply can make them seem truthful or lying.
Almighty God uses abundant irony and incongruity to make a point. We are all familiar with the story of the naming of our second patriarch Isaac (Yitzhak) meaning laughter (Genesis 21:5-6). Earlier in Genesis 18:10-15, when God informed Abraham and Sarah that they will have a son “by this time next year,” Sarah openly laughs incredulous that she would ever experience sexual pleasure again—really? An 89-year-old? Abraham was even more over the hill, 99 years old, reproductively speaking dead (Hebrews 11:11-12). Consider the incredible irony of this miracle—from a post-menopausal woman and a man probably riddled with ED come descendants as numerous as the stars and countless as the sands of the seashore (Genesis 15:5, Genesis 22:17, Genesis 26:14, Exodus 31:13).
Sarah's relationship with God lacked honesty and trust and faith at that moment, which is revealed in her fearful lying response to God's promise.
