Sayyiduna Abu Dharr (may Allah be pleased with him) narrates: I swear by Allah that this verse: "These are two opposing groups who disputed concerning their Lord" [Al-Hajj: 19] was revealed concerning these six: Hamzah, Ubaydah and Ali bin Abi Talib (may Allah be pleased with them), and Utbah and Shaybah, the two sons of Rabi'ah, and al-Walid bin Utbah. These men had faced each other in single combat on the day of Badr.
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2941