What is the saying of the Messenger of Allah, peace and blessings be upon him, regarding the man who fought fiercely then killed himself, after the Prophet, peace and blessings be upon him, said about him: "Verily, he is among the people of Hellfire"?

The aforementioned Hadith in the question was narrated by Al-Bukhari and Muslim. The meaning of the Prophet's (PBUH) saying: "And a man may do the deeds of the people of Paradise, in the eyes of the people" refers to what appears to people from the outward aspect of his deeds. For he may, in his inner self, be a disbeliever, a hypocrite, or a show-off. This includes everyone who outwardly displays goodness but inwardly conceals evil. Al-Hafiz Ibn Hajar mentioned that it is interpreted as referring to a hypocrite or a show-off. Al-Hafiz Ibn Rajab indicated that the inner reality of the matter may be contrary to what appears to people, citing as evidence the Hadith in Muslim about a man who fought fiercely but was among the people of Hell because he killed himself. And Allah strengthens this religion even with a wicked man.