The article Muhammad, Islam, and Sex discusses various aspects of this vast topic, Islam and Sexual Perversions as some more aspects.
Muhammad is believed by Muslims to have had the strength of 30 or 40 men when it came to sex, cf. Muhammad's Sexual Prowess.
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Narrated 'Aisha:
Sa'd bin Abi Waqqas and 'Abd bin Zam'a quarrelled with each other (regarding a child). The Prophet said, "The boy is for you, O 'Abd bin Zam'a, for the boy is for (the owner) of the bed. O Sauda ! Screen yourself from the boy." The sub-narrator, Al-Laith added (that the Prophet also said), "And the stone is for the person who commits an illegal sexual intercourse." (Sahih Bukhari 8.807)
Narrated Abu Huraira:
The Prophet said, "The boy is for (the owner of) the bed and the stone is for the person who commits illegal sexual intercourse.' (Sahih Bukhari 8.808)
Muhammad, however, married the wife of his adopted son, Zaid. However, adoption is prohibited in the Qur'an (al-Ahzab 33:4-5)