We've already solved the Mystery of Muhammad's Death, so that cold case is closed. But there is another mystery in early Islam, which we'll call "Sheepgate: The Case of the Qur'an's Missing Verses on Breastfeeding Adults."
In order to solve this mystery, we'll need some background information.
Take, for instance, Muhammad's solution to the problem of a man and a woman, who aren't married to each other, needing to be alone together for some reason. How would an unmarried man and woman avoid having sex at the first opportunity? Not a problem, when you've got Allah at your beck and call. Allah, in his timeless wisdom, revealed in the Qur'an that the woman simply needs to breastfeed the man ten times, which will make them legally related (she will be his foster mother). That way, they won't be tempted to have sex.
Even though the Qur'an is eternal, however, Allah eventually changed his eternal mind about the need for ten breastfeedings. Five, it turns out, would be sufficient:
Sahih Muslim 3422—Amra reported that she heard Aisha discussing fosterage which (makes marriage) unlawful; and she (Aisha) said: There was revealed in the Holy Qur'an ten clear sucklings, and then five clear (sucklings).
So five breastfeedings were enough to turn a man into a woman's foster son, and therefore to eliminate the possibility of sexual relations.
But be careful to complete at least five breastfeedings, because one or two wouldn't be enough, as Muhammad was careful to point out:
Sahih Muslim 3417—Allah's Apostle said: Being suckled once or twice, or one suckling or two, do not make marriage unlawful.
So there we have it. The Qur'an contains at least two verses on breastfeeding adults—one abrogated verse requiring ten breastfeedings and another verse requiring five. Aisha is quite clear that these verses are part of the Qur'an:
Sahih Muslim 3421—Aisha reported that it had been revealed in the Holy Qur’an that ten clear sucklings make the marriage unlawful, then it was abrogated by five sucklings and Allah’s Apostle died and it was before that time (found) in the Holy Qur’an (and recited by the Muslims).
But these verses aren't in the Qur'an we have today. So what happened to them? Aisha tells us what happened to the first verse:
Sunan ibn Majah 1944—It was narrated that Aishah said: “The Verse of stoning and of breastfeeding an adult ten times was revealed, and the paper was with me under my pillow. When the Messenger of Allah died, we were preoccupied with his death, and a tame sheep came in and ate it.”
The other verse (commanding five breastfeedings) isn't in the Qur'an either, so we can only conclude that both verses on breastfeeding adults were eaten by Aisha's sheep. Was this a mere accident, or was something more sinister afoot? Let's see if we can solve the Mystery of the Missing Verses.
For a while at least, Muhammad's wives were on board with Allah's views concerning breastfeeding and fosterage, for Muhammad's wife Hafsa ordered her sister to breastfeed Asim before he could visit her:
Al-Muwatta of Imam Malik 30.1.8—Yahya related to me from Malik from Nafi that Safiyya bint Abi Ubayd told him that Hafsa, Umm al-Muminin [Mother of the Believers], sent Asim ibn Abdullah ibn Sa'd to her sister, Fatima bint Umar ibn al-Khattab, for her to suckle him ten times so that he could come in to see her. She did it, so he used to come in to see her.
Eventually, however, most of Muhammad's wives (everyone except Aisha, who was happy to have her sister breastfeed men for her, in order to make them her foster brothers) became disgruntled over the practice, and they insisted that Allah's command to breastfeed adults didn't apply to them:
Al-Muwatta of Imam Malik 30.2.12—Sahla bint Suhayl, who was the wife of Abu Hudhayfa, and one of the tribe of Amr ibn Lu'ayy, came to the Messenger of Allah, and said, "Messenger of Allah! We think of Salim as a son and he comes in to see me when I am uncovered. We only have one room, so what do you think about the situation?" The Messenger of Allah said, "Give him five drinks of your milk and he will be mahram [illegal to marry] by it." She then saw him as a foster-son. Aisha, Umm al-Muminin [Mother of the Believers], took that as a precedent for whatever men she wanted to be able to come to see her. She ordered her sister, Umm Kulthum bint Abi Bakr as-Siddiq and the daughters of her brother to give milk to whichever men she wanted to be able to come in to see her. The rest of the wives of the Prophet refused to let anyone come in to them by such nursing. They said, "No, by Allah! We think that what the Messenger of Allah ordered Sahla bint Suhayl to do was only by an indulgence concerning the nursing of Salim alone. No, by Allah! No-one will come in upon us by such nursing!"
Apparently, Muhammad's wives had more common sense than their husband, for they realized how silly it was for grown women to put their bare breasts into the mouths of grown men in an attempt to avoid sexual tension.
So what happened to the missing verses?
There are only three plausible explanations for why these verses were eliminated from the Qur'an when Muhammad died. First, since Aisha had the only written copy of the verses, Muhammad's other wives may have eventually persuaded her to destroy them. Second, while Aisha may have remained faithful in her desire to preserve the Qur'an, Muhammad's other wives may have engaged in a bit of sabotage, sending a hungry sheep into Aisha's house to rid the world of one of history's most ridiculous teachings. Third, Sheepgate may have been a genuine accident; Aisha's sheep may have coincidentally consumed a verse that most of Muhammad's wives found absolutely repulsive.
I find the third explanation the least probable, since it would be extraordinarily unlikely for a sheep to start munching on such an absurd verse by chance. The first two explanations may seem to be equally plausible, since they both account for the data. Nevertheless, there's another important piece of data to consider. The sheep didn't only eat the verse of breastfeeding an adult, but also the verse of stoning an adulteress. Because Aisha had been accused of adultery, we don't need Sherlock Holmes to tell us what she would have thought of that verse.
The evidence, then, points to sabotage, either by Aisha alone or by some conspiracy among Muhammad's wives. The verses of breastfeeding an adult, along with the verse of stoning, fell victim to one of history's least common means of malice: death by sheep.
For more on this topic, see Sam Shamoun's article: "Islam and the Nursing of Adults."