It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him), who said: The Messenger of Allah (peace and blessings be upon him) entered (Makkah) on the occasion of Umrat al-Qada', and Abdullah bin Rawahah (may Allah be pleased with him) was walking in front of him reciting this rajaz: "O sons of the disbelievers, clear the way for him (the Messenger of Allah (peace and blessings be upon him)); indeed the Most Merciful has revealed in His Revelation that the best death is to be killed in His path."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14011