Surah An-Nahl 16:105

الَّذِينَ لاَ يُؤْمِنُونَ بِآيَـتِ اللَّهِ

(Verily, those who do not believe in Allah's Ayat,) Allah will not guide them, and theirs will be a painful punishment, meaning, the disbelievers and heretics who are known to the people as liars. The Messenger Muhammad ﷺ, on the other hand, was the most honest and righteous of people, the most perfect in knowledge, deeds, faith and conviction. He was known among his people for his truthfulness and no one among them had any doubts about that - to such an extent that they always addressed him as Al-Amin (the Trustworthy) Muhammad. Thus when Heraclius, the king of the Romans, asked Abu Sufyan about the attributes of the Messenger of Allah ﷺ, one of the things he said to him was, "Did you ever accuse him of lying before he made his claim" Abu Sufyan said, "No". Heraclius said, "He would refrain from lying about people and then go and fabricate lies about Allah"

Ayat ini menyanggah tuduhan orang-orang kafir yang mengatakan bahwa Al-Qur'an adalah ciptaan Muhammad. Sesungguhnya yang membuat-buat kebohongan itu bukan Rasul saw, tetapi orang-orang yang tidak beriman kepada ayat-ayat Allah, baik ayat-ayat kauniyah yang menjelaskan keesaan dan kekuasaan Allah yang terdapat pada alam semesta ini, maupun ayat-ayat qur'aniyah yang memberi petunjuk dalam kehidupan ini. Jadi sebenarnya mereka yang menjadi pendusta, bukan Rasul saw karena beliau adalah orang yang paling jujur, sempurna ilmu dan amal perbuatannya, kuat keyakinan, dan paling terpercaya. Karena kejujuran dan kebersihan jiwanya, ia diberi nama al-Amin (orang yang jujur).