Sahih Muslim Book 009, Hadith Number 3564.
Chapter: Li'an (Invoking curse).
'Abdullah reported: We were on the night of Friday staying in the mosque when a person from the Ansar came there and said: If a person finds his woman along with a man, and he speaks about it, you would lash him, and if he kills, you will kill him, and if he keeps quiet he shall have to consume anger. By Allah, I will definitely ask about him from Allah's Messenger (may peace be upon him). On the following day he came to Allah's Messenger (may peace be upon him) and asked him thus: If a man were to find with his wife a man and if he were to talk about it, you would lash him; and if he killed, you would kill him, and if he were to keep quiet, he would consume anger, whereupon he (the Holy Prophet) said: Allah, solve (this problem), and he began to supplicate (before Him), and then the verses pertaining to li'an were revealed: "Those who accuse their wives and have no witnesses except themselves" (xxiv. 6). The person was then put to test according to these verses in the presence of the people. There came he and his wife in the presence of Allah's Messenger (may peace be upon him), and they invoked curses (in order to testify their claim). The man swore four times in the name of Allah that he was one of the truthful and then invoked curse for the fifth time saying: Let there be curse of Allah upon him if he were among the liars. Then she began to invoke curse. Allah's Messenger (may peace be upon him) said to her: just wait (and curse after considering over it), but she refused and invoked curse and when she turned away, he (Allah's Apostle) said: It seems that this woman shall give birth to a curly-haired black child, And so she did gave birth to a curly-haired black child.