What is the ruling on a father's action of selling his house to his stepchildren without leaving anything for his daughters, especially since one of the daughters is paralyzed?

This sale does not deviate from two scenarios:

The first: It is a real sale concluded by your father while he was sane, mature, and acting of his own free will. This sale is valid, and he has the right to dispose of his property. He is obligated to provide suitable housing for his household.

The second: It is a fictitious sale, a trick to favor some children and deprive others. This action is not permissible, and your father is sinful for it, due to the Prophet’s (peace and blessings of Allah be upon him) prohibition of favoring some children over others, unless there is a legitimate reason such as need or illness.

If the sale was a trick and was done by word of mouth but the house was not handed over until death or deathbed illness, then it is rejected by the consensus of the imams. The fact that it was phrased as a sale does not affect this, because what matters are the meanings and intentions.

If the father handed over the house during his lifetime and while in good health, then there is a difference of opinion among scholars regarding the validity of such a gift. The preponderant view is that it is not valid, due to the explicit command of the Prophet (peace and blessings of Allah be upon him) to return gifts that involve favoritism, and because it engenders animosity and hatred among the children.