“may Allah have mercy on you.” How, then, can you reply, “May Allah guide us and guide you,” putting yourself before him in the supplication? If he had instead said, “May Allah have mercy on us and on you,” you could answer, “May Allah guide us and guide you.” But since he said exactly what he was instructed to say—“May Allah have mercy on you”—you must respond as you have been instructed: “May Allah guide you and set your affairs right.”

It is related that some Jews would deliberately force themselves to sneeze in the presence of the Prophet—peace and blessings be upon him—hoping that he would say to them, “May Allah have mercy on you.” They knew he was a prophet and thought that his supplication for mercy might benefit them. Yet it does not benefit them, for a prayer of mercy on behalf of a disbeliever avails him nothing. Indeed, it is impermissible to ask Allah’s mercy or forgiveness for them once they have died. Allah the Exalted says, “It is not for the Prophet and those who believe to seek forgiveness for the polytheists—even if they are close relatives—after it has become clear to them that they are people of Hellfire” (Qur’an, 9:113).

Someone might object: “Did not Abraham seek forgiveness for his father, while Abraham was himself a pure monotheist?” The answer is found in Allah’s words: “Abraham’s request for forgiveness for his father was only because of a promise he had made to him. But when it became clear to him that his father was an enemy of Allah, he disassociated himself from him. Truly Abraham was tender-hearted and forbearing” (Qur’an, 9:114).

When people uphold all of these mutual rights laid down by the Prophet—peace and blessings be upon him—harmony and affection flourish among them, and the grudges and resentments that lurk in hearts and souls disappear.