To Florus 5.10

After this he passed over the whole continuous discussion of Abraham and Sarah, who received a son as a gift when their bodies were already as good as dead (Romans 4:19; Genesis 21:1–2). Even an ordinary reader, not only a wise one, understands how strongly their example supports the truth. He passed it over by saying it carried little weight against him. At least this statement, framed as follows, should have recalled him from such shamelessness: ‘To bring this argument’s main point to a brief conclusion: if the child whom God promised was given through sexual desire, then what fulfilled God’s pledge was undoubtedly good. If he was given without sexual desire, desire cannot harm the offspring, since it was present neither when he was conceived nor when he was born.’