All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.

It is unlawful for a father to show favoritism among his children — whether sons or daughters — in a gift, if this is driven by his own displeasure with the sharī‘ah distribution of inheritance. Whoever does this while believing the sharī‘ah distribution to be unjust places himself in grave danger, based on the words of Allah, Glorified and Exalted is He {which mean}: "Then is it the judgment of [the time of] ignorance they desire? But who is better than Allah in judgment for a people who are certain [in faith]?" [al-Mā'idah/50]. Shaykh Muḥammad al-Khalīlī ash-Shāfi‘ī (raḥimahullāh) said: "Whoever is called to [accept] the ruling of the Sharī‘ah and refuses, his condition cannot be other than one of several possibilities — among them, that he is displeased with what Allah, the Exalted, and His Messenger have ruled. There is no dispute regarding the disbelief (kufr) and apostasy (riddah) [entailed] in such a case." [Fatāwā al-Khalīlī, Vol.2/P.221]

Some scholars of fiqh have held that certain contracts are not valid when the person entering into them is predominantly motivated by the intent to deprive certain heirs of their inheritance. It is stated in al-Fatāwā al-Fiqhiyyah al-Kubrā (Vol.3/P.256), by the verifying scholar Imam Ibn Ḥajar al-Haytamī (raḥimahullāh): "He was asked regarding someone who established a waqf (religious endowment) exclusively for his male children, to the exclusion of his female children, with the specific intention of depriving them [of a share]. Is such a waqf valid?

He answered: If we stipulate that a valid waqf requires the intention of drawing closer to Allah — which is the position that the Imam [an-Nawawī] attributed to the majority — then this waqf would not be valid, and this is the fatwā given by a group [of scholars], including ‘Umar al-Fatā, his student al-Kamāl ar-Raddād, and others. But if we stipulate only that the waqf must be free from involving a sin, then it would be valid — provided we hold that intending to deprive an heir through a disposition made while in good health is not itself unlawful. However, the general implication of the ḥadīth that has been narrated — 'Whoever cuts off a prescribed share of inheritance, Allah will cut off his share of Paradise' — suggests that such an act is unlawful."

Those scholars who held that contracts involving the intent to deprive certain heirs are nonetheless valid still maintained that such contracts are not free of sin. Imam Ibn Ḥajar al-Haytamī (raḥimahullāh) was also asked: "Regarding a person who established a waqf for his male children only, excluding the females — and it is highly likely that he intended to deprive them of inheritance, since certain people from a particular region tend to do this when the endower grows elderly and death draws near, resulting in harm to the daughters through their exclusion from inheritance — and some scholars have issued fatwās upholding the validity of this practice — kindly clarify this matter for us.

He answered: If this waqf was made during a terminal illness, then it is treated as a bequest to an heir, and it is only enforceable if the [other] daughters consent to it; if they reject it, it is invalidated. But if it was made while the person was in good health, then it is valid — even if he intended thereby to deprive his heirs. The most this intention entails is that he bears a sin for it, but this does not necessitate the invalidation of the waqf itself, since [the sinful intent] is a matter external to the transaction itself. And Allah knows best." [al-Fatāwā al-Fiqhiyyah, Vol.3/P.244]

Shaykh Muḥammad al-Mashhūr ash-Shāfi‘ī (raḥimahullāh) said: "Scholars have differed regarding someone who makes a vow benefiting some of his children to the exclusion of others: al-Fatā, ar-Raddād, Ibn Ziyād, and al-Qammāṭ held that it is not valid, since a valid vow requires the intention of drawing closer to Allah, and this [preferential] act is disliked — a position affirmed by an-Nawawī in Tanqīḥ al-Wasīṭ. However, if the preference is given due to some legitimate additional merit that justifies the distinction — such as one child being in particular need, or possessing some special virtue — then it is valid. Ibn Ḥajar, Abū Makhramah, and Yūsuf al-Muqri' held the view that it is valid without qualification, arguing that the element of dislike stems from an external factor [i.e., the underlying intent], much like the dislike associated with perpetual fasting [which does not invalidate the fast itself].

I [the author] say: this discussion, as you can see, concerns someone who singles out some of his children [with a vow]. However, if someone makes a vow benefiting certain heirs to the exclusion of others of an entirely different category — such as someone who makes a vow for his children but excludes his parents or spouse — then this is valid by unanimous agreement, even if intended to deprive them, contrary to the view of al-Qammāṭ. That said, it is not free of being disliked, especially if the intent to deprive is apparent — indeed, it may even be inwardly unlawful in such a case, so take heed." [Bughyat al-Mustarshidīn, Vol.3/P.701]

Accordingly: it is unlawful for a father to show favoritism among his children in gift-giving with the intention of rejecting the sharī‘ah distribution of inheritance. Indeed, he places himself in grave danger {Holding him to account on the Day of Judgment} by harboring such an intention. And Allah, the Exalted, knows best.