وَسَجَدَ وُجُوبًا بِمَا صَلُبَ مِنْ أَنْفِهِ وَبِجَبْهَتِهِ، وَلَا يَصِحُّ الِاقْتِصَارُ عَلَى الْأَنْفِ إِلَّا مِنْ عُذْرٍ بِالْجَبْهَةِ
The preferred ruling taught by the matn requires prostration with the forehead and the firm part of the nose. Restricting Sujud to the nose alone is not valid when the forehead can be used; a genuine forehead excuse is the exception.