#said in his heart

"thought to himself" or "said to himself silently"

#Can a child be born to a man who is a hundred years old?

Abraham used this rhetorical question because he did not believe that this could happen. AT: "Surely a man who is a hundred years old cannot father a child." (See: [[:en:ta:vol1:translate:figs_rquestion]])

#And can Sarah, who is ninety years old, bear a son?

Again Abraham used a rhetorical question because he did not believe this could happen. The phrase "who is ninety years old" tells why Abraham did not believe that Sarah could bear a son. This can be expressed as a separate sentence: "And Sarah is ninety years old. Could she bear a son?" or "And Sarah is ninety years old. Surely she could not bear a son." (See: [[:en:ta:vol1:translate:figs_rquestion]] and  [[:en:ta:vol2:translate:figs_distinguish]])

#Oh that Ishmael might live before you

Abraham suggested something that he believed really could happen. AT: "Please let Ishmael inherit the covenant that you have made with me" or "Perhaps Ishmael could receive your covenant blessing."