The last instruction the Messenger of Allah ﷺ gave was when he said, "Two religions shall not be left in the Arabian Peninsula."
كان آخر ما عهد رسول الله ﷺ أن قال: لا يترك بجزيرة العرب دينان.
Narrated by Ahmad (26352) and Tabarani in Awsat (2691, Majmaal-Bahrayn), both by way of Ibn Ishaq, who said, Salih bin Kaysan told me, from Zuhri, from Ubaydullah bin Abdullah bin Utba, from Ayesha, and he related it. Its chain is hasan because of Muhammad bin Ishaq. Haythami said in Majma (5/325), "The men of Ahmad's chain are the men of the Sahih, apart from Ibn Ishaq, and he has explicitly stated that he heard it directly."Malik also narrated it in Jami (17), from Ibn Shihab, that the Messenger of Allah ﷺ said, "Two religions shall not coexist in the Arabian Peninsula." But Ibn Abdul-Barr affirmed that this hadith is established through several hasan routes from the Prophet ﷺ, among which he mentioned the hadith of Ayesha. See Tamhid (12/13).