Is a 65-year-old man's belief in magic and his claim that his deceased brother's wife practiced magic on his daughter considered a form of polytheism (shirk), and what is the recompense for those who err in this matter, and how can one who errs repent?

If the intent behind describing a man as believing in magic is that he believes in its existence and its effect by Allah's permission, then there is no harm in that, for magic is a reality and has an effect. What is forbidden, however, is accusing people of magic without evidence, or believing sorcerers in their claims of knowing the unseen. The latter falls under a severe warning, as the Prophet, peace and blessings be upon him, said: "Three will not enter Paradise: a habitual drunkard, one who severs ties of kinship, and one who believes in magic." Believing a sorcerer in his lies is considered disbelief, as Ibn Mas'ud said: "Whoever comes to a sorcerer, or a soothsayer, or a diviner, and believes him in what he says, has disbelieved in what was revealed to Muhammad." It is not permissible to accuse anyone of magic except with clear evidence, and dreams are not considered such evidence. One must repent if they have accused someone based on assumptions. It is also recommended to strive for reconciliation between disputing parties.