Ibnu ^Asakir narrated that Imam Abul-Hasan al-Ash^ariyy saw the Prophet in a dream ordering him to support the school of Ahl us-Sunnah wal-Jama^ah.
Imam Abul-Hasan al-Ash^ariyy was astonishing in his ability to produce the proofs to discredit the innovators of misguidance.
Imam Abu ^Abdullah Ibn Khafif, who was one of the great waliyys said:
"When I was a young man, I went to al-Basrah to meet Abul-Hasan al-Ash^ariyy because I heard about him. When I first entered al-Basrah, I saw a handsome shaykh. I asked him, "Where is the residence of Abul-Hasan al-Ash^ariyy?"
He said, "What do you want from him?"
I said: "I would like to meet him."
This shaykh told me, "Come back tomorrow morning to this same location, and I shall help you with that."
I came the next morning, and went with that shaykh to a session in the house of a prominent person. Present in that session were several scholars and knowledgeable people. When the people saw that shaykh come in, they treated him respectfully and seated him in the best and most prominent location in that session. Then, one of the people there was asked a question pertaining to the creed. When that person started responding, this shaykh interfered and began to debate the one who was asked the question--until he silenced him. I was astonished by the extent of that shaykh’s knowledge, so I asked some of those who were near to me who this shaykh was. They told me this was Abul-Hasan al-Ash^ariyy. When the session was over and the people left, I followed him.
He looked at me and asked, "Young man, how did you find Abul-Hasan al-Ash^ariyy?"
I said, "Just as I have heard about him, and I am your servant." Then I asked Imam al-Ash^ariyy, "Why did you not start talking yourself?"
Imam al-Ash^ariyy said, "I do not initiate talking with those innovators of misguidance. but once they have uttered deviated thought it becomes obligatory on me to give the correct answer"
Imam al-Ash^ariyy did not initiate talking with innovators because he did not want to open a door for them to speak unlawful words. He would not, however, allow them to get away with speaking unlawful words should they initiate them. Rather, he would debate them and refute them in accordance with what Allah obligated us to do in forbidding the unlawful (munkar) and ordering the obligatory (ma^ruf). This showed a great level of understanding and comprehension.