Explanation of the mawquf hadith: The athar of Hudhayfah, who said: (No group has ever exchanged curses without the curse becoming a right upon them). It is authentic.

The Shaykh : Therefore, the author (may Allah have mercy on him) followed the two preceding hadiths with the following athar, namely the mawquf hadith which he also narrated with a valid chain from Hudhayfah, who said: "No group has ever exchanged curses without the curse becoming a right upon them".
"No group has ever exchanged curses" means they cursed one another, some of them cursing others with curses without right, except that they thereby became deserving of the curse of Allah (Blessed and Exalted is He). This confirms that what the sincere and the martyars purify themselves from is cursing without right.