The Messenger of Allah ﷺ announced to the people the death of Najashi on the very day he died. He took them out to the prayer ground, arranged them in rows, and said four takbirs over him.
حدثنا القعنبي قال قرأت على مالك بن أنس عن ابن شهاب عن سعيد بن المسيب
أن رسول الله ﷺ نعى للناس النجاشي في اليوم الذي مات فيه وخرج بهم إلى المصلى فصف بهم وكبر أربع تكبيرات
Bukhari narrated it in the Book of Funerals, chapter "A man announcing the death to the family of the deceased himself," hadith no. 1245, and Muslim narrated it in the Book of Funerals, chapter "On takbir over the funeral," hadith no. 951, both from the hadith of Malik through the same chain, and it is found in Muwatta (Yahya narration) 1/226, 227.