In verse 4:22 of the Holy Quran Allah (swt) has forbidden Muslim men to marry their step- mothers. With this ruling the Quran has brought to an end the cruel and repulsive custom, prevalent in the Jahilliyah period, which allowed men to marry their step-mother after the death of their father.
In order to understand the Quranic ruling mentioned in the verse 4:3 we will have to delve into history. During the Jahilliyah period the guardians of the orphan girls used to get lured by their wealth and beauty into marrying them. However, they would not pay these orphans the dower/meher. So Allah (swt) has forbidden the Muslim men (in verse 4:3) from marrying the orphans if they are not able to behave with them in a just manner. Instead they are free to marry other women. They can marry one, two, three or (maximum) four women, if they want, on the condition that they will behave with all of them in a just manner. Prophet Mohammad (saw) had married more than 4 times. However, the Muslim Ummah is not supposed to emulate the Prophet (saw) in this matter because his marriages are amongst the khasais –e-Mustafa. Hence, if the Muslim men are uncertain about being equitable towards all their wives, so they should marry only once or resort to slave-girls.
In verse 4:4 Allah (saw) has ordered the Muslim men to offer the dower (obligatory bridal money offered to a wife by the husband at the time of their marriage) to their wife willingly. If they part with some of the dower with their own pleasure, then the men can enjoy it with wholesome result.
Keep Me In Your Prayers.