{Note: The sentence inside parentheses is the Saudi...
Ibn Asakir has mentioned the above tradition attributed to Ali, in whose chain of authority is Ibn Saa'ed. Then he wrote: "Ibn Saa'ed is a LIAR". Also other such as Darqunti mentioned that these traditions are single. (See Ifraad, by Darqunti). If the Prophet has forbidden the temporary marriage FOREVER in the Day of Khaibar (1/7 AH), why it was practiced even after the battle of Hunain (after 10/8 AH) with the direct order of the Prophet?
(See the reference above) In other words: How is that possible that one is forbidden FOREVER and in two different points of time, in the Day of Khaibar (1/7 AH) and on the victory Mecca (9/8 AH) FOREVER, and people were practicing it between these two instants of time and after these two instances with the order of the Prophet? In the mentioned tradition about the battle of Hunain, it is said that the messenger of Allah ALLOWED to do Mut'a for after the battle of Hunain.
So we can not say people did it because they did not know it was forbidden forever. The traditions confirms that Mut'a was done with the direct order of the Prophet. So how can we justify these few alleged traditions that the Prophet forbade it forever before that? This contradiction itself supports the fact that all these few narrations were made up to cover up and to justify what Umar enforced during his rule based on his idea.
How nice is the verse 4:82 of Quran describes that one can find many contradictions in something that is not from Allah. Two Sunni scholars: al-Qurtubi (in his commentary of Quran) and al- Nawawi (in his commentary of Sahih Muslim) are in the opinion that different traditions concerning the ban of Mut'a specify seven different dates!!! How is that possible that people after the demise of the Prophet were practicing it?
To answer this, some claim that although the Messenger of Allah had forbidden it, but it had not been given wide publicity, and thus some continued to practice it till Umar reinforced that law during his rule.