Is it permissible for a wife to say to her husband: "By the right of my love for you, you should not do such and such." Is it permissible for anyone to say so to someone whom he loves?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

If saying this is intended for swearing, then it is impermissible because the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, forbade Muslims to swear by other than Allaah The Almighty. It is narrated that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said: “If anyone has to swear, let him swear by Allaah otherwise let him remain silent.” [Al-Bukhari, Muslim and others]

But, if saying this is meant to make the husband’s love a means to obtain a purpose, there will be no objection, Allaah Willing. In this case, saying this is considered a form of appeal, or insistent demand of what the person needs by way of solicitation and reminding of love. There is also no blame, Allaah Willing, to entreat someone by the right of kinship ties to do or to not do something.

Allaah Knows best.