Keeping the word (Say) is a great evidence that Prophet Muhammad (saws) can never change a single letter in the Holy Quran. Had the Quran been by the Prophet as claimed by the enemies of Islam, the Prophet would have crossed out the word (Say).

(… قُل لِّلَّذِينَ كَفَرُوا سَتُغْلَبُونَ ) (Say to those who disbelieve, “You will be overcome …): Allah (swt) states that faith will prevail:

 {وَقُلْ جَاءَ الْحَقُّ وَزَهَقَ الْبَاطِلُ ۚ إِنَّ الْبَاطِلَ كَانَ زَهُوقًا}

(And say, “Truth has come, and falsehood has departed. Indeed is falsehood, [by nature], ever bound to depart.”) (Al-Israa: 81)

There are always two parties: faith and polytheism, disbelief, and corruption on earth as well as an ongoing conflict between the right and the falsehood. The right will prevail subsequently. This verse is a proof on the same. When Prophet Muhammad (saws) entered Mecca in the Year of Conquest, he used to point towards the statues around the Kaaba with a small stick in his hands, and the statues were destroyed immediately. This is another proof that the falsehood will be defeated by wisdom, argument, evidence, and proof:

 {قُلْ هَاتُوا بُرْهَانَكُمْ إِن كُنتُمْ صَادِقِينَ}

(Say, “Produce your proof, if you should be truthful.”) (An-Naml: 64)

rather than by swords.

(… وَتُحْشَرُونَ إِلَىٰ جَهَنَّمَ …) (…and gathered together to Hell …): The Day of Gathering is the day when Allah the Almighty brings all creatures together for reckoning and reward. In that day, hell is the destiny of the disbelievers.

( وَبِئْسَ الْمِهَادُ … ) (…and wretched is the resting place.”): How wretched is the resting place the disbelievers are destined to.