Sahih Bukhari Volume 9, Book 88, Hadith Number 225.

Narrated By Al-Hasan Al-Basri : When Al-Hasan bin ‘Ali moved with army units against Muawiya, ‘Amr bin AL-As said to Muawiya, “I see an army that will not retreat unless and until the opposing army retreats.” Muawiya said, “(If the Muslims are killed) who will look after their children?” ‘Amr bin Al-As said: I (will look after them). On that, ‘Abdullah bin ‘Amir and ‘Abdur-Rahman bin Samura said, “Let us meet Muawaiya and suggest peace.” Al-Hasan Al-Basri added: No doubt, I heard that Abu Bakra said, “Once while the Prophet was addressing (the people), Al-Hasan (bin ‘Ali) came and the Prophet said, ‘This son of mine is a chief, and Allah may make peace between two groups of Muslims through him.”