In Shu'bah's narration (Abu al-Siddiq) said: I was present with Ibn Umar (may Allah be pleased with them both) when he placed a deceased person in the grave, and he said: "Bismillah wa 'ala millati Rasulillah" (In the name of Allah, and upon the religion of the Messenger of Allah (peace and blessings be upon him)).
It has also been narrated through another route from Ibn Umar as marfu' with additional words, but it is weak.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 7060