This sermon has been quoted before, however with a different narration
So now, certainly Allah deputised Muhammad (S.A.) as the Prophet while no one among the Arabs read the Book nor claimed prophethood or revelation. He had to fight those who disobeyed him in company with those who followed him, leading them towards their salvation and hastening with them lest death overtook them. When any weary person sighed or a distressed one stopped he stood at him till he got him his aim, except the worst in whom there was not virtue at all. Eventually he showed them their goal and carried them to their places (of deliverance). Consequently, their affairs moved on and their hand-mill began to rotate , their spears got straightened.
By Allah, I was among their rear-guard till they turned back on their sides and were flocked in their rope. I never showed weakness or lack of courage, nor did I betray or become languid. By Allah, I shall split the wrong till I extract right from its flanks.