According to Islamic scholars, if a person combines a missed fardh prayer with sunnah or rawatib prayer using one intention, then neither of the two prayers will be valid. This is because both types of prayers are separate acts of worship. Combining them means mixing fardh (obligatory) and nafl (voluntary) prayers, which makes the salah invalid.

Imam Al-Ramli explained that joining two prayers like fardh and sunnah with one takbir (opening) and one intention does not make the prayer valid. Likewise, Ibn Baz stated that combining a sunnah prayer with tahiyyat al-masjid (greeting of the mosque) is allowed, but combining two separate sunnah or fardh prayers with one intention is not allowed.