The concepts were introduced into Islam during the Arab expansion of the 7th century, due to cross-pollination of Jewish and Christian parables and theology into Islam, called "Isra'iliyyat". Some medieval Muslim writers—including Muhammad ibn Jarir al-Tabari, Ibn Khaldun, and even the later "Book of the Zanj"—asserted the view that the effects of Noah's curse on Ham's descendants included blackness, slavery, and a requirement not to let the hair grow past the ears, despite the fact that this contradicted the teachings of the Islamic prophet Muhammad regarding skin color and racial equality, most notably in his last sermon. This is also in spite of the fact that the account of the drunkenness of Noah and curse of Ham are not present within the text of the Quran, the Islamic holy book, and not consistent with Islamic teachings that Noah is a prophet, and prophets do not drink alcohol. Islam holds prophets of God in very high esteem, and some Muslims suggest the prophets are infallible.