One of his wives, Zaynab, was originally his adopted son’s wife. Muhammad asked Zaid to divorce her and give her to him. When he refused, Muhammad had a revelation that commanded Zakl to give her up and decreed that there was no evil in a man taking his daughter-in-law from his adopted son.
In contrast, when David fell into the temptation of another man’s wife, God punished him severely.
2 Samuel 12:10-14 (NIV) “10 Now, therefore, the sword will never depart from your house, because you despised me and took the wife of Uriah the Hittite to be your own.’ 11 “This is what the Lord says: ‘Out of your own household I am going to bring calamity on you. Before your very eyes I will take your wives and give them to one who is close to you, and he will sleep with your wives in broad daylight. 12 You did it in secret, but I will do this thing in broad daylight before all Israel.’”13 Then David said to Nathan, “I have sinned against the Lord.” Nathan replied, “The Lord has taken away your sin. You are not going to die. 14 But because by doing this you have shown utter contempt for[a] the Lord, the son born to you will die.”
Another of his wives, Aesha, was only 6 years old when he married her and only 8 or 9 when he consummated the marriage. She later became his favorite wife. He died in her lap. In some Islamic countries even today a girl of that age can be given to an adult male for a wife.
Muhammad died in 632 after a sudden illness. Some believe a Jewish woman poisoned him because his armies had murdered her relatives. He had named no successor. This caused a major conflict that continues even until today. The major division in Islam is between the Sunni and Shiite. They are divided over who was the rightful successor to Muhammad. Shiite means partisan. Shiites believe only the descendants of Muhammad through Fatima can be imams. They believe that these imams, (They are divided as to whether there are 7 or 12), are sinless, miracle workers, and infallible. About 80%-90% of Muslims are Sunni. Shiites are the majority only in Iran. Sometimes one group will persecute the other.