10 Then one of them said, "I will surely return to you about this time next year, and Sarah your wife will have a son." Now Sarah was listening at the entrance to the tent, which was behind him. 11 Abraham and Sarah were already very old, and Sarah was past the age of childbearing. 12 So Sarah laughed to herself as she thought, "After I am worn out and my lord is old, will I now have this pleasure?" 13 Then the Lord said to Abraham, "Why did Sarah laugh and say, 'Will I really have a child, now that I am old?' 14 Is anything too hard for the Lord? I will return to you at the appointed time next year, and Sarah will have a son." 15 Sarah was afraid, so she lied and said, "I did not laugh." But he said, "Yes, you did laugh."

Matthew Henry's Commentary on Genesis 18:10-15

Commentary on Genesis 18:9-15

(Read Genesis 18:9-15)

Where is Sarah thy wife? was asked. Note the answer, In the tent. Just at hand, in her proper place, occupied in her household concerns. There is nothing got by gadding. Those are most likely to receive comfort from God and his promises, who are in their proper place, and in the way of their duty, 17; but He who searches the heart, saw that the one sprung from unbelief, and the other from faith. She denied that she had laughed. One sin commonly brings in another, and it is not likely we shall strictly keep to truth, when we question the Divine truth. But whom the Lord loves he will rebuke, convict, silence, and bring to repentance, and if they sin before him.