Assalaamo alaykum, is Abu Al-Hasan Al-Ash‘ari from the Salaf (righteous predecessors) or the Khalaf (latter-day Muslims)?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger. 

Perhaps you are asking about Abu Al-Hasan Al-Ash‘ari 'in terms of his Creed. If this is the case, then the answer is that he passed through three phases in this regard:

The First: the phase of the Mu‘tazilites. In this phase, he was affected by his step-father, Abu ‘Ali Al-Jubbaa'i, and he adopted the belief of Mu‘tazilites along with him until the age of forty. Then he disassociated himself from him, as he did not find convincing answers to some of the issues he asked him about.

The Second: the Kullaabiyyah phase. It is a phase during which he was inclined to the methodology of Ibn Kullaab and his ideology. This phase is the one adopted by the Ash‘arites today, as we have already highlighted in fatwas 5719 and 39878.

The Third Phase: It is the phase in which he adopted the ideology of the Salaf. This is evident in some of his books, such as his book Al-Ibaanah, where he clarified in its introduction that he is affiliated to Imaam Ahmad ibn Hanbal in belief. This is also evident in his book Risaalah ila Ahl Ath-Thaghr, and Maqaalaat Al-Islaamiyyeen. All this proves the ideology which he finally adopted and followed.

Allah knows best.