Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: When the companions of Ali (may Allah be pleased with him), as they set out towards Basrah, received the news that the people of Basrah had gathered in support of Talhah and al-Zubayr (may Allah be pleased with them both), it weighed heavily on them and settled in their hearts. Ali (may Allah be pleased with him) said: By the One besides whom there is no god, we will surely prevail over the people of Basrah, Talhah and al-Zubayr will surely be killed, and there will surely come out to you from Kufah six thousand five hundred and fifty men, or five thousand five hundred and fifty men (this doubt is from the narrator al-Ajlah). Ibn Abbas (may Allah be pleased with them both) said: This settled in my mind. Then when the people of Kufah arrived, I went out and said to myself: I will certainly see; if it is as he said, then it is something he heard, otherwise it is a stratagem of war. So I met a man from the army and asked him, and by Allah, without any delay he said exactly what Ali (may Allah be pleased with him) had said. Ibn Abbas (may Allah be pleased with them both) said: And this was among the things that the Messenger of Allah (peace and blessings be upon him) used to tell him.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10692