He said, "The Sunnah in the funeral prayer is to recite the Mother of the Quran silently after the first takbir, then to say three more takbirs, with the salutation given at the last one."
أخبرنا قتيبة قال حدثنا الليث عن ابن شهاب
أنه قال السنة في الصلاة على الجنازة أن يقرأ في التكبيرة الأولى بأم القرآن مخافتة ثم يكبر ثلاثا والتسليم عند الآخرة
Sourcing, sahih. Ibn Jarud narrated it, no. 540, from the hadith of Ibn Shihab Zuhri at length, and it is in Kubra, no. 2116. Zuhri explicitly stated that he heard it directly, and Ibn Mulaqqin declared it sahih in Tuhfat al-Muhtaj, no. 788, as did Ibn Hajar and others.It has another route in Tahawi's Maani al-Athar, 1/500, from the hadith of Abu Umama, from a man among the companions of the Prophet. Hakim declared it sahih, 1/360, according to the criteria of the two Shaykhs, and Dhahabi agreed with him. He also narrated it from the hadith of Habib bin Salama in similar wording.