If one combines the fast of Saturday with Sunday, the dislike disappears, for there is then no imitation of either group. This is what Ḥadith 578 indicates: fasting both days runs contrary to the practice of adherents of both religions, since each community venerates one of the two days but not both together.

Shaykh al-Islam said: The proofs from the Qur’an and Sunnah, as well as consensus and sound reasoning, all demonstrate that imitating the disbelievers is forbidden. Thus it is unlawful for Muslims to imitate them in anything specific to their festivals—whether food or drink, clothing or bathing, lighting fires, suspending normal routines of livelihood or worship, or any similar matter. Equally impermissible is abandoning established vocations, crafts, or trade, or treating the day as one of rest, joy, and play in a way that distinguishes it from the days before and after. It is likewise forbidden to prepare banquets, exchange gifts, or display adornments on such a day. The guiding rule is that it must remain like any other day.

Ibn al-Qayyim said: The scholars are unanimous that it is prohibited to give gifts on the disbelievers’ religious festivals or to congratulate them on the feasts by which they worship Allah, for such actions pose a grave danger that may lead to disbelief. Therefore, a Muslim should deliberately differ from the People of the Book in their festivals and acts of worship, just as the Prophet—peace and blessings be upon him—used to fast Saturday and Sunday intentionally to oppose the idolaters among the People of the Book.