Taking God at His Word
Genesis 18:14 (ESV) …. ‘Is anything too hard for the Lord? At the appointed time I will return to you, about this time next year, and Sarah shall have a son.”
Contextual verses: Genesis 18:9-15
We have an example of unbelieving laughter in Genesis 18 in the account of God’s appearance to Abraham at the trees of Mamre. The visitors had arrived in the heat of the day, and Abraham had at once set about to provide a noon meal for them. As they ate, the visitors asked about Sarah. Abraham replied that she was in the tent, where it was proper for her to be in accord with oriental custom. This led to the promise spoken by the one visitor who was the Lord himself: “I will surely return to you about this time next year, and Sarah your wife will have a son” (v. 10a).
Sarah had been listening to the men’s conversation and so heard this seemingly impossible promise. The text says, “Now Sarah was listening at the entrance to the tent, which was behind him. Abraham and Sarah were already old and well advanced in years, and Sarah was past the age of childbearing. So Sarah laughed to herself as she thought, ‘After I am worn out and my master is old, will I now have this pleasure?’ ” (vv. 10b–12). This laughter was different from the laughter of Abraham recorded in the previous chapter, which was the laughter of joyful acceptance or at least of wonder mixed with growing belief. Sarah’s laughter was an expression of utter unbelief, as the response of the Lord indicates.
“Then the Lord said to Abraham, ‘Why did Sarah laugh and say, “Will I really have a child, now that I am old?” Is anything too hard for the Lord?’ ” (vv. 12–14).
Notice three things about this unbelief. First, unbelief is sin. I do not know if, at this point, Sarah or Abraham realized that their visitors were from heaven or that the one visitor was the incarnate God. If Sarah had realized this, her unbelief would have been more reprehensible. But even if she had not, it was still inexcusable, for God had promised many times that Abraham and Sarah would have a son. He had recently given special and solemn testimony to this (Gen. 17:15–16). So to laugh as Sarah did was to say that God was a liar and could not be trusted.
Consider the apostle John’s clear denunciation of unbelief: “We accept man’s testimony, but God’s testimony is greater because it is the testimony of God, which he has given about his Son. Anyone who believes in the Son of God has this testimony in his heart. Anyone who does not believe God has made him out to be a liar, because he has not believed the testimony God has given about his Son” (1 John 5:9–10). We tend to treat a lack of faith lightly. But, as John Stott says, “Unbelief is not a misfortune to be pitied; it is a sin to be deplored. Its sinfulness lies in the fact that it contradicts the word of the one true God and thus attributes falsehood to him.”
Second, like all sin, unbelief leads to other sins. It is a case of chain reaction. When God confronted Sarah for her unbelief, she might have made excuses, saying that her laughter was actually an expression of joy in God’s promise or that she was only laughing as Abraham had when God made the same promise to him earlier (Gen. 17:17). Each of those excuses would have been untrue, of course. But Sarah did something even worse: she lied outright, saying, “I did not laugh” (v. 15). This is why sin is so serious and why we cannot willingly sin even “just a little bit.” The only safe course is to repudiate sin entirely and turn to him who is faithful and just to provide both forgiveness and cleansing (1 John 1:9).
Third, God does not treat unbelief lightly. This is obvious from the nature of unbelief itself, for if unbelief is sin and if it leads to other sins, unbelief is clearly an offense to God and must be dealt with firmly. This principle is also vividly illustrated in the episode. Sarah had laughed to herself, so that even Abraham, her husband, did not hear it. But God did. Before him, all hearts are open, all desires known, and he replied at once with a question designed to expose and correct the transgression: “Why did Sarah laugh and say, ‘Will I really have a child, now that I am old?’ Is anything too hard for the Lord?” A moment later, after Sarah had lied about laughing, God said, “Yes, you did laugh” (vv. 13–15).
This seems harsh to us. We sin, and hope that God will ignore the sin. Then we are puzzled when the details of our lives go badly and prayer seems like pounding against a stone wall. How slow we are to learn! Has God not said, “Surely the arm of the Lord is not too short to save, nor his ear too dull to hear. But your iniquities have separated you from your God; your sins have hidden his face from you, so that he will not hear” (Isa. 59:1–2). Many millions are hindered and even miserable in their Christian lives simply because they will not deal with sin severely, as God does.
 Boice, J. M. (1998). Genesis: an expositional commentary (pp. 605–607). Grand Rapids, MI: Baker Books.