Sunan an-Nasa'i 2893
It was narrated that Anas said:
"The Prophet entered Makkah during Umratul-Qada' and Ibn Rawahah went before him, saying: 
Get out of his way, you unbelievers, make way.
Today we will fight about its revelation
With blows that will remove heads from shoulders
And make friend unmindful of friend.
Umar said to him: "O Ibn Rawahah! In the Sanctuary of Allah and in front of the Messenger of Allah you recite poetry?" The Prophet said: "Let him do that, for by the one in whose hand is my soul, his words are harder for them than being shot with arrows."
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ الْمَلِكِ بْنِ زَنْجُويَهْ، قَالَ حَدَّثَنَا عَبْدُ الرَّزَّاقِ، قَالَ حَدَّثَنَا جَعْفَرُ بْنُ سُلَيْمَانَ، عَنْ ثَابِتٍ، عَنْ أَنَسٍ، قَالَ دَخَلَ النَّبِيُّ صلى الله عليه وسلم مَكَّةَ فِي عُمْرَةِ الْقَضَاءِ وَابْنُ رَوَاحَةَ بَيْنَ يَدَيْهِ يَقُولُ خَلُّوا بَنِي الْكُفَّارِ عَنْ سَبِيلِهِ الْيَوْمَ نَضْرِبْكُمْ عَلَى تَأْوِيلِهِ ضَرْبًا يُزِيلُ الْهَامَ عَنْ مَقِيلِهِ وَيُذْهِلُ الْخَلِيلَ عَنْ خَلِيلِهِ قَالَ عُمَرُ يَا ابْنَ رَوَاحَةَ فِي حَرَمِ اللَّهِ وَبَيْنَ يَدَىْ رَسُولِ اللَّهِ صلى الله عليه وسلم تَقُولُ هَذَا الشِّعْرَ فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏
"‏ خَلِّ عَنْهُ فَوَالَّذِي نَفْسِي بِيَدِهِ لَكَلاَمُهُ أَشَدُّ عَلَيْهِمْ مِنْ وَقْعِ النَّبْلِ ‏"‏ ‏.‏