In a time when marrying more than one woman was a norm, Islam came to set limitations and protect the rights of the women. In Chapter 4 (Surah an-Nisaa), verse 3, after allowing the Muslim men to marry two, three or four wives, the Qur’ãn immediately says:

“but if you fear that you will not do justice (between them), then (marry) only one…” (Surah an-Nisaa, 4:3)
 
This is a very important ayah to consider.

While Allah has allowed men to take more than one wife, HIS commands are explicitly clear in saying a man can do so ONLY if he is able to treat them in a just manner.

Now what does this mean?

It means one man must be able to fulfill his matrimonial duties towards his wives equally. The duties involve
1. Fulfilling her emotional needs
2. Fulfilling her physical needs
3. Fulfilling her financial needs
4. Fulfilling her spiritual needs

Only exceptional people are capable of being just and fair, in this context. The Qur’ãn itself, in the same Chapter 4, verse 129, says:
 
“And you do not have the ability to do justice between the wives, even though you may wish (to do so)…” (Surah an-Nisaa, 4:129)

If the man is unable to create a sense of fairness and justice between his wives. Then Khalaas! That's it. He must strictly marry only one.

And Allah knows best.

@Umm_e_Meeran @aakhirq @Fahad_Heaven I hope this brings in some context to the ayah and helps this discourse on polygyny.

May Allah guide us.