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