"You will never be able to deal equitably between (your) wives...
"You will never be able to deal equitably between (your) wives, however much you be eager (to do so); then do not incline with a total inclination (to one) so that you leave her as it were in suspense; and if you effect reconciliation and keep from evil, then verily Allah is Forgiving, Merciful." Heavenly Law Has no Contradiction with Natural Disposition It is natural that a man shows more affection to his young wife than his aged wife.
That is why the commandment of Justice is only due to the treatment of man unto his wives, not due to his heartily love. "You will never be able to deal equitably between (your) wives...." Now that heartily justice is not possible, then, there should be equity in action. In Islam, there is no duty beyond the ability of a person. A human being is not usually able to adjust affection, but he is able to apply justice in dealing the affairs. It is unlawful for a man to leave his wife undecided. "...
"Yet if they (should) separate, Allah will enrich each out of His abundance, and Allah is All-Embracing, the Wise." Next to the former discussion, in this verse it points to this fact that if he continuation of conjugal life is tiresome for the couple and there have come forth some things that the circumstance can never be remediable, they do not have to continue such a marriage and to be prisoner of a bitter family life like that.
They can separate from each other and, without having any fear from their future, they should decide bravely, because in this condition, if they separate, Allah will enrich both of them out of His abundance and Mercy. They can be hopeful to have better spouses and more delightful lives in future. "Yet if they (should) separate, Allah will enrich each out of His abundance...." This situation exists, because Allah has a vast inclusive Mercy and abundance, together with Wisdom. It says: "...