[4:129] You will never be able to be just to your wives, even if you be eager; yet do not turn altogether away, so that you leave her like one suspended. If you set things right, and fear, surely God is ever Forgiving, Merciful.
It means when you are concerned for yourself in your affairs, the situation is reflected back on you, and the soundness of your union becomes the reverse by a corruption on your part. But when you have made God your concern in your affairs, your way of living will become balanced and the moment will be cleared of turmoil.
It is said whomever God has determined to be deficient in intellect in his state, you are not able to set their deficiency right by your ability.
Yet do not turn altogether away: It means do not deviate from the clear path of the command. Stop where you have been made to stop and do what you have been commanded to do.
So that you leave her like one suspended: It means that you when you prevent them from the companionship of others and then cut them off from their shares with you, you cause them harm in two ways: there is nothing to be had from you nor is there any way to someone else. Surely this harm is great. The allusion in this is to the fact that when the path to your worldly concerns is blocked to you, He (s) opens the witnessing of His right to you and the finding of His kindness. Surely whoever's annihilation is in God, the Real is his substitute. If you make right what is between you and other people, and put your trust in what is between you and the Real, surely God will be forgiving of your failings and merciful in pardoning your sins.