It is narrated from Sayyiduna Anas (may Allah be pleased with him) that when the Prophet (peace and blessings be upon him) entered Makkah, Sayyiduna Abdullah bin Rawahah (may Allah be pleased with him) walked in front of the Messenger of Allah (peace and blessings be upon him) reciting these verses: "O sons of the disbelievers, clear his way; today we will strike you over its interpretation, a blow that removes the head from its resting place and makes a friend forget his friend." Sayyiduna Umar (may Allah be pleased with him) said: "O Ibn Rawahah, in front of the Messenger of Allah (peace and blessings be upon him) and in the Sanctuary of Allah you recite poetry?" Thereupon the Messenger of Allah (peace and blessings be upon him) said: "O Umar, leave him. By the One in whose hand is my soul, these verses are harder on them than the blows of swords."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14012