My question is: The standpoint of the Shi’a regarding the Quranic verse, “فانکحوا ما طاب لکم من النساء مثنی وثلاث ورباع” is that it means 18 wives, but Ahlus-Sunna’s standpoint is that it means 4 wives. Please clarify this with evidence.
According to Ahlus-Sunna, it is permissible to have only four wives as per Shari’ah. It is not permissible to have more than four. The clear texts of Holy Quran and Ahadith supports this standpoint, and the Sahaba and Tabieen is also of this view. The mentioned verse has also been explained with this meaning by Ibn Abbas and most scholars. Furthermore, wherever the words “مثنی وثلاث ورباع” appear in the Holy Quran or in Arabic idioms, it means “two, three and four”, and nothing else. In Sura-Al-Furqan, Allah mentions about the creation of angels by saying:
الحمد للہ فاطر السماوات والارض جاعل الملائکۃ رسلا اولی اجنحۃ مثنی وثلاث ورباع یزید فی الخلق ما یشاء ان اللہ علی کل شیء قدیر
Translation: All praise is due to Allah, the originator of the heavens and earths, the one who made angels his messengers possessing wings, two, three and four. He increases in his creation whatever he will. Indeed Allah is capable of all things.
There are many incidents mentioned in Ahadith about some of the Sahaba having more than four marriages during the pre-Islamic times when they were disbelievers, then when they and all of their wives accepted Islam, the Holy Prophetﷺ ordered them to choose any four of their wives to keep in their marriage and leave off the rest, and they did as was ordered. However, with regards to the Holy Prophetﷺ himself, he was exempted from this law. This was something specific to him.
Other people who claims that having 18 wives at one time, or Rawafidh (Shi’ah) who claim that having 9 wives at one time is permissible, they base their claims on the what the Holy Prophetﷺ did (which was specific to him), and it is not proper to use that as an evidence (for their claim). Some references from Tafseer and Ahadith has been briefly mentioned below. For more details, one can also refer to books of Tafseer.