Authentic
Sunan an-Nasa'i 1989
"The Sunnah, when offering the funeral prayer, is to recite Umm Al-Qur'an) the Exxence of the Qur'an) quietly in the first Takbir, Then to say three (more) Takbir and to say the Taslim after the last one."
السُّنَّةُ فِي الصَّلاَةِ عَلَى الْجَنَازَةِ أَنْ يَقْرَأَ فِي التَّكْبِيرَةِ الأُولَى بِأُمِّ الْقُرْآنِ مُخَافَتَةً ثُمَّ يُكَبِّرَ ثَلاَثًا وَالتَّسْلِيمُ عِنْدَ الآخِرَةِ .