Verse 17 gives the second response of Abraham to God’s words of promise, the first being in Gen 17.3.

Then Abraham fell on his face: see discussion of Gen 17.3. Since this is the second time that Abraham has responded in this way, some translations say “Abraham bowed right down to the ground again.”

And laughed: in order to avoid giving the impression that Abraham was so amused that he fell down laughing, it will often be necessary to separate the act of reverent submission from the laughter that follows. Good News Translation does this effectively with “but he began to laugh when he thought.” The Hebrew verb translated laughed has an even wider range of meaning than the English word, and in some contexts it is better translated “played” or “smiled.” However, many languages have a range of different terms for laughing that are used in different situations or suggest different attitudes and feelings in the ones who laugh. In translation it is important to use a term that is appropriate to Abraham’s emotion in this context: this is a laugh of disbelief, not of amusement; and Abraham probably did not have a smiling face, which is what the common word for “laugh” would suggest in a number of languages.

Translators should notice that the word “laugh” occurs a number of times and has a prominent place in the story of the birth of Isaac. It describes the reaction of both Abraham and Sarah when the birth of a child is promised, here in 17.17 and again in 18.12, 13, 15. It comes again in 21.6, when the promise is fulfilled. And the name given to the child (17.19; 21.3) is Isaac, which means “he laughs.” As far as possible the word “laugh” should be rendered in the same way each time it occurs throughout this story.

And said to himself is literally “and said in his heart.” This may be translated “and asked himself in his heart,” “asked himself,” “thought to himself,” “questioned in his innermost.” Typical translations say “But he laughed and thought like this” or “He laughed to himself and said.” One translation changes the order of laughing and thinking into what seems to be the natural order, and says “… but he was thinking, I will be a hundred and I can’t have a child; and Sarah is… And when he thought like that he laughed.”

Shall a child be born to a man who is a hundred years old?: Abraham’s question reflects his surprise that God would even consider an aged couple having a child. The question is rhetorical: Abraham is not asking if it is possible, but rather he is saying emphatically that it is not possible. In some languages this question must be answered “No, of course not.” If a rhetorical question is inappropriate in this context, it may be expressed as a negative statement; for example, “It is not at all possible for a hundred-year-old man to become a father.”

Shall Sarah, who is ninety years old, bear a child?: this question can be handled in the same manner as the one concerning Abraham. Alternatively translators may wish to combine the two questions and say, for example, “Can I who am a hundred years old and Sarah who is ninety have a child? Of course not!” or “I am a hundred years old and Sarah is ninety; how can we have a child? It is impossible!”

One quite colloquial translation that expresses the feeling of disbelief well says “I’m a hundred and he reckons I’m going to have a son of my own. And my wife Sarah is a really old woman of ninety, and he reckons she’s going to have a baby. We-two can’t!”

Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .