Muslims tend to justify the numerous marriages of Muhammad by telling that they were political motivated and were meant to make alliances with various groups. Furthermore they point at the fact that most of his wives were widows.
The story of Kinana and Safiya is a cynical example of one of those marriages where Muhammad actually ordered the killing of the husband of Safiya after which he married her. So Safiya became a widow indeed. The alliance of Muhammad with the tribe of Safiya did not materialise as he killed most of the members of her tribe.
The events took place after Muhammad made an unprovoked attack on the rich Jewish tribe of Khaybar of which Kinana and Safiya were members. Muhammad led a Muslim force against the Khaybar oasis, which was inhabited by Jews -- many of whom he had previously deported from Medina.
In his biography of Muhammad Ibn Ishaq writes on page 511:
“When the apostle raided a people he waited until the morning. If he heard a call to prayer he held back; if he did not hear it he attacked. We came to Khaybar by night, and the apostle passed the night there; and when morning came he did not hear the call to prayer, so he rode and we rode with him….We met the workers of Khaybar coming out in the morning with their spades and baskets. When they saw the apostle and the army they cried, ‘Muhammad with his force,’ and turned tail and fled. The apostle said, ‘Allah Akbar! Khaybar is destroyed. When we arrive in a people’s square it is a bad morning for those who have been warned.’”
The torture and killing of Kinana, the husband of Safiya is detailed on page 515:
Kinana b. Al-Rabi’, who had the custody of the treasure of B. Al-Nadir, was brought to the apostle who asked him about it. He denied that he knew where it was. A Jew came to the apostle and said he had seen Kinana going round a certain ruin every morning early. When the apostle said to Kinana, “Do you know that if we find you have it I shall kill you?” he said Yes. The apostle gave orders that the ruin was to be excavated and some of the treasure was found. When he asked him about the rest he refused to produce it, so the apostle gave orders to al-Zubayr b. Al-’Awwam, “Torture him until you extract what he has,” so he kindled a fire with flint and steel on his chest until he was nearly dead. Then the Apostl delivered him to Muhammad b. Maslama and he struck off his head, in revenge for his brother Mahmud.
Kinana’s wife was taken as a war prize; Muhammad claimed her for himself and hastily arranged a wedding ceremony that night. He halted the Muslims’ caravan out of Khaybar later that night in order to consummate the marriage.
The following traditions by Bukhari give more details:
Narrated Anas bin Malik: “We arrived at Khaibar, and when Allah helped His Apostle to open the fort, the beauty of Safiya bint Huyai bin Akhtaq whose husband had been killed while she was a bride, was mentioned to Allah's Apostle. The Prophet selected her for himself, and set out with her, and when we reached a place called Sidd-as-Sahba,' Safiya became clean from her menses then Allah's Apostle married her. Hais (i.e. an 'Arabian dish) was prepared on a small leather mat. Then the Prophet said to me, "I invite the people around you." So that was the marriage banquet of the Prophet and Safiya. Then we proceeded towards Medina, and I saw the Prophet, making for her a kind of cushion with his cloak behind him (on his camel). He then sat beside his camel and put his knee for Safiya to put her foot on, in order to ride (on the camel).“
The Prophet stayed for three rights between Khaibar and Medina and was married to Safiya. I invited the Muslim to his marriage banquet and there wa neither meat nor bread in that banquet but the Prophet ordered Bilal to spread the leather mats on which dates, dried yogurt and butter were put. The Muslims said amongst themselves, "Will she (i.e. Safiya) be one of the mothers of the believers, (i.e. one of the wives of the Prophet ) or just (a lady captive) of what his right-hand possesses" Some of them said, "If the Prophet makes her observe the veil, then she will be one of the mothers of the believers (i.e. one of the Prophet's wives), and if he does not make her observe the veil, then she will be his lady slave." So when he departed, he made a place for her behind him (on his and made her observe the veil.
According to the Quran, his marriage with Safiya was invalid because after the death of her husband, Safiya could only get married after a waiting period of 4 months and ten days.
2.234. If any of you die and leave widows behind, they shall wait concerning themselves four months and ten days: When they have fulfilled their term, there is no blame on you if they dispose of themselves in a just and reasonable manner. And Allah is well acquainted with what ye do.
This means that a widow has to wait a number of menstruation cycles to make sure she is not pregnant. Muhammad only waited until her ongoing menses were over, married her and consummated the marriage. So according to the laws instated by Muhammad, the marriage was invalid and as a married man he should have been stoned to death for consummating this invalid marriage. Muhammad seems not to have felt bound by the precepts of the Quran if it did not fit his cause.
Did Muhammad have the torture and assassination of Kinana and the “marriage” to his wife immediately thereafter in mind when he said: “I have been made victorious by terror”?