This is war. Daesh vs. al Qaeda
The international terrorist group Daesh has published the message of their "official Shariah spokesperson" and also the chief of the group's operation in Syria Abu Mohammad al-Adnani to the al Qaeda leaders in the current issue of the English-language Daesh magazine Dabiq.
It seems that Daesh does not welcome al Qaeda at its territory, even though both organizations have been fighting side by side, regarding the recent news. Anyway, in spite of the seeming respectful tone, the message resembles ultimatum. And some passages are offensive not only for common Muslims, but even for such Wahhabis as al Zawahiri or al Julani.
Could it be that after their leader's death, Daesh has made a decision to get rid of their main rival and to unite former al Qaeda branches under their banner?