ENOfficial
Abu Ishaq said: Al-Harith left his will that Abdullah ibn Yazid should offer his funeral prayer; so he prayed over him. He then put him in the grave from the side of his legs and said: This is a Sunnah (model practice of the Prophet).
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُعَاذٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي إِسْحَاقَ، قَالَ أَوْصَى الْحَارِثُ أَنْ يُصَلِّيَ، عَلَيْهِ عَبْدُ اللَّهِ بْنُ يَزِيدَ فَصَلَّى عَلَيْهِ ثُمَّ أَدْخَلَهُ الْقَبْرَ مِنْ قِبَلِ رِجْلَىِ الْقَبْرِ وَقَالَ هَذَا مِنَ السُّنَّةِ .
sunnah.com