Hazrat Abu Hurairah (ra) relates that once he had the chance to spend the night with the Holy Prophet Muhammad (sa). The Holy Prophet (sa) started the recitation with ‘Bismillah’ [in the name of Allah]; he started to cry and fell down crying. Afterwards he recited ‘Bismillah’ twenty times and every time he would fall down weeping. Later on he told me that a person on whom the Gracious and Merciful God does not show mercy, is very unfortunate.
A delegation from Kindah tribe came to visit the Holy Prophet (sa). They requested him to show them a sign of his truthfulness. The Holy Prophet Muhammad (sa) presented the Holy Qur’an as a miraculous sign and said that it was such a discourse which cannot be influenced by falsehood, neither from behind nor from the front. Then he recited first six verses of Surah al-Saffat in a melodious tone.
وَٱلصَّـٰٓفَّـٰتِ صَفّٗا *فَٱلزَّـٰجِرَٰتِ زَجۡرٗا *فَٱلتَّـٰلِيَٰتِ ذِكۡرًا *إِنَّ إِلَٰهَكُمۡ لَوَٰحِدٞ *رَّبُّ ٱلسَّمَٰوَٰتِ وَٱلۡأَرۡضِ وَمَا بَيۡنَهُمَا وَرَبُّ ٱلۡمَشَٰرِقِ 
These verses mean; ‘In the name of Allah the Gracious, the Merciful, By those who range themselves in close ranks. Then they drive away the enemy vigorously. Then they recite Qur’an as a Reminder. Surely Your God is One, Lord of the heavens and the earth and all that is between them. And the Lord of the sun’s risings.’ 
The Holy Prophet (sa) stopped here as his voice was choking with emotion. He sat motionless and in silence. The tears were flowing from his eyes and falling on his beard. The people from Kindah tribe were amazed to see this and said, ‘So you cry out of fear of the One Who has sent you?’ The Holy Prophet (sa) replied, ‘Yes, His fear makes me cry, the One Who commissioned me on Sirat-e-Mustaqim (the absolutely straight path). I have to follow it perfectly straight. It is like the edge of the sword and if I deflect a tiny bit, I will be destroyed.
. The Holy Qur’an, 37:2-6.
Muhammad (sa) – The Perfect Man (Qadian, India: Nazarat Isha’at, 2015), 132-134.