What is the ruling on a man writing all his property to his son, to the exclusion of his daughters, except for one orchard which the daughters refused to accept?

It is not permissible to favor one child over another in gifts, whether male or female, without a legitimate Sharia-compliant reason. Such an act is an injustice forbidden by Allah. The proof for this is the hadith of Nu'man ibn Bashir, in which the Prophet, peace and blessings be upon him, refused to bear witness to a father's injustice in favoring some of his children in gifts. Favoring males over females merely because they are female is a characteristic of the Age of Ignorance (Jahiliyyah). Therefore, the father must repent and rectify this injustice by distributing fairly. The most apparent opinion is that it is obligatory to equalize between male and female in gifts, based on the hadith: "Make equality between your children in gifts, for if I were to favor anyone, I would have favored women."