2- Tranquillity...
2- Tranquillity: Allah, to whom belong Might and Majesty, said: "And among His great Signs is that He created for you mates from among yourselves so that you get tranquillity by them and He has put love and mercy between your (hearts); verily in that are Signs for those who reflect." (Quran 30:21) The goals for marriage mentioned in the above verse are: achieving spiritual stability, social and psychological tranquillity, and love and mercy to each other.
These goals can be attained by both permanent and temporary marriages. 3- Providing an alternative way to avoid the sin of fornication: "Successful indeed are the believers... those who abstain from sex, except with those joined to them in the marriage bond or with the slave girls whom they rightfully possess for (in their case) they are free from blame.
But those who go beyond that are transgressors." (Quran 23:1-7) The traditions of the Prophet (PBUH&HF) provide other reasons for marriage, one of which is: 4- Protecting one's religion: The Messenger of Allah said: "The one who gets married earns half/(one third) of his religion, and therefore, he should fear God for the other half/(two third)." Temporary marriage has safeguarded many good believers (both brothers and sisters), and has protected them from falling into the hands of evil and sin, and has persevered their faith and religion.
Also "spreading Islam" could be another goal for marriage. In this case, however, the temporary marriage is less risky than the permanent marriage. And there are many more reasons and goals for marriage. Mut'a vs. Alcohol To justify the practice of Mut'a at the time of the Prophet (PBUH&HF), some people assert that similar to the way that Allah prohibited Alcohol gradually, Mut'a was allowed but it was forbidden gradually before the demise of the Prophet.
Other than the fact that many companions and their disciples (see part III for the list of their names) were promoting Mut'a long after the demise of the Prophet, which clearly contradicts above proposal, we should say that there is no similarity between the case of Alcohol and Mut'a. Alcohol was known before Islam for many centuries and Islam did not legislate nor legitimized it.
This is while Mut'a with the Islamic regulations surrounding it was not known before Islam, and Islam legitimized it and defined its rules. The Prophet NEVER PROMOTED to drink Alcohol from the beginning of his mission to its end, but he promoted Mut'a.