Is it permissible for a man married to more than one woman to declare his love for one of them, or should this love remain in the heart and not be shown?

A man's open declaration of loving one wife more than others does not contradict the justice he is obliged to maintain among his wives. The justice required of him is in lodging and sustenance, according to what is customary. As for justice in love and sexual intercourse, it is not obligatory. Ibn Qudamah said: "Equality is not obligatory between them in enjoyment through anything less than sexual intercourse, such as kissing, touching, and the like, because if equality is not obligatory in sexual intercourse, then it is even more so for its preludes."