Abu Dawud Book 8, Hadith Number 2641.
Narated By Abdullah ibn Umar : Ibn Umar was sent with a detachment of the Apostle of Allah (PBUH). The people wheeled round in flight. He said: I was one of those who wheeled round in flight. When we stopped, we said (i.e. thought): How should we do? We have run away from the battlefield and deserve Allah’s wrath. Then we said (thought): Let us enter Medina, stay there, and go there while no one sees us. So we entered (Medina) and thought: If we present ourselves before the Apostle of Allah (PBUH), and if there is a change of repentance for us, we shall stay; if there is something else, we shall go away. So we sat down (waiting) for the Apostle of Allah (PBUH) before the dawn prayer. When he came out, we stood up to him and said: We are the ones who have fled. He turned to us and said: No, you are the ones who return to fight after wheeling away. We then approached and kissed his hand, and he said; I am the main body of the Muslims.