What is the authenticity of the hadith: "Whoever's head is split open in the cause of Allah and he seeks his reward from Him, all his previous sins will be forgiven"? And is it permissible to advise with it and speak about its virtue?

This hadith was narrated by Sa'id ibn Mansur, Al-Bazzar, and Al-Tabarani. Its chain of narration contains weakness, which is why Al-Suyuti indicated its weakness, and Al-Albani declared it weak. However, some scholars, like Al-Haythami and Al-Mundhiri, deemed it good (hasan). Therefore, there is no objection to mentioning it in the chapter on encouragement and virtues, as it is among the hadiths concerning the virtues of deeds, in which leniency is permitted.