How can you leave off the Sunnah of your Prophet and take the saying of Fulān (so and so)?

🎙Shaykh al-‘Allāmah Ṣāliḥ bin Fawzān bin ‘Abdillāh al-Fawzān حفظه الله

https://www.dropbox.com/s/de0io42pdado6i9/ShFawzan_sunnahorFulan.mp4?dl=0