"I said: 'O Messenger of Allah! Surah Al-Hajj has been esteemed by two prostrations?' He said: 'Yes, and whoever does not prostrate for them, he should not recite them.'" (Using translation from Tirmidhī 578)
سَمِعْتُ عُقْبَةَ بْنَ عَامِرٍ يَقُولُ قُلْتُ يَا رَسُولَ اللَّهِ أَفُضِّلَتْ سُورَةُ الْحَجِّ بِسَجْدَتَيْنِ؟ قَالَ «نَعَمْ فَمَنْ لَمْ يَسْجُدْهُمَا فَلَا يَقْرَأْهَا»