Fatwa ID: 05632
Answered by: Mufti Eunus Ali
Why did the Prophet Muhammad PBUH marry Safiya RA before the prescribed iddah period?
In the name of Allah, the Most Gracious, the Most Merciful
To begin with, it is narrated by Anas bin Malik RA: the Prophet (ﷺ) came to Khaibar and when Allah SWT made him victorious and he conquered the town by breaking the enemy’s defence, the beauty of Safiya bint Huyai bin Akhtab was mentioned to him and her husband had been killed while she was a bride. Allah’s Messenger (ﷺ) selected her for himself and he set out in her company till he reached Sadd-ar-Rawha’ where her menses were over and he married her. Then Hais (a kind of meal) was prepared and served on a small leather sheet (used for serving meals). Allah’s Messenger (ﷺ) then said to me, “Inform those who are around you (about the wedding banquet).” That was the marriage banquet given by Allah’s Messenger (ﷺ) for (his marriage with) Safiya RA. After that, we proceeded to Medina and I saw that Allah’s Messenger (ﷺ) was covering her with a cloak while she was behind him. Then he would sit beside his camel and let Safiya put her feet on his knees to ride (the camel).
Secondly, in Islam when a person becomes the owner of a female prisoner of war before he is able to be intimate with her he is required to ensure that she is not pregnant. The method of this is by waiting until she completes one menstrual cycle and thereafter it will be permissible for the two to be intimate. 
Thirdly, initially, Safiyah (may Allah be pleased with her) was taken as a prisoner of war before the Prophet of Allah (peace be upon Him) married her, hence after completing only one menstrual cycle she was permitted for the Prophet of Allah (peace be upon Him) to marry and be intimate with her.
In the Hadith the phraseفَبَنَى بِهَاis used. The Arabic linguist Ibnul Atheer has stated that this phrase is used when a husband consummates the marriage with his wife. 
We learn from this that after Safiyah had completed her menstrual cycle, the Prophet (peace be upon Him) had definitely married her and thereafter consummated the marriage.
It is also Narrated by Anas RA: Allah’s Messenger (ﷺ) freed Safiyah and then married her, and her Mahr was her manumission, and he gave a wedding banquet with Hais (a sort of sweet dish made from butter, cheese and dates).
Conclusion: the normal iddah which is prescribed to a divorced woman does not apply here as Safiyahs (may Allah be pleased with her) situation was different with her initially being a prisoner of war.
In this day and age as slavery is scarce, the Islamic laws surrounding them have also become uncommon and therefore can sometimes lead one to confusion if they are not aware of them.
Only Allah knows best
Written by Mufti Eunus Ali
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Saheeh Bukhari: 2235
 Raddul Muhtar, Volume 9, Page 539, Darul Kutubul Ilmiyyah
 UmdatulQari, Volume 12, Page 74, Darul Kutubul Ilmiyyah
 Saheeh Bukhari: 5169