Does the action of the questioner's father in building stones in a place that a woman claimed contained the tomb of a righteous saint, lighting candles and incense there, and the woman's annual visit to it, constitute polytheism, and what should the questioner do about it?

It is impermissible to construct shrines and mausoleums over graves, or to light candles on them, or to hold festivals and feasts; all of these are reprehensible innovations. Likewise, embarking on journeys specifically to visit the graves of saints is, according to the preponderant opinion, impermissible. And among the practices observed by people at these shrines are those that are forbidden, such as seeking to make supplication at the grave, and interceding with Allah through the deceased. And among them are those that constitute polytheism (shirk (definition)), such as supplicating the saints, circumambulating their graves, and offering vows to them. The questioner should advise her father and relatives with wisdom and good counsel, encouraging them to demolish this structure.