Ja'far bin Muhammad (may Allah have mercy on him) narrates from his father that in the time of the Messenger of Allah (peace and blessings be upon him) water was sprinkled on the grave.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6739
Ja'far bin Muhammad narrates from his father that the Messenger of Allah (peace and blessings be upon him) sprinkled water on the grave of (his son) Ibrahim and placed pebbles on it. Al-Shafi'i (may Allah have mercy on him) says: Pebbles stay only on a level grave.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6740
Abdullah bin Muhammad bin Umar (may Allah have mercy on him) narrates from his father that the Messenger of Allah (peace and blessings be upon him) sprinkled water on the grave of Ibrahim (may Allah be pleased with him), and it was the first grave on which water was sprinkled; and when he had finished burying him, he said: 'Salamun alaykum' (Peace be upon you). And I do not know except that he (also) said: He threw soil on it with his hands.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6741
Abdullah bin Muhammad bin Umar (may Allah have mercy on him) narrates that his father (may Allah have mercy on him) said: The Messenger of Allah (peace and blessings be upon him) sprinkled water on the grave of his son. And he says: I do not know otherwise than that he (also) threw soil on it with his hands.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6742
Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) narrates that water was sprinkled on the grave of the Prophet (peace and blessings be upon him), and the one who sprinkled the water on it was Sayyiduna Bilal bin Rabah (may Allah be pleased with him). He began with a water-skin from the head side, on the right side of the grave, until he reached the feet. Then he threw the water towards the wall, because he could not go around from the wall's side.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6743