Pouring water over a grave after leveling earth over it

Q 2: What is the purpose of pouring water over a grave after leveling earth over it? Is there any evidence for this practice and who was the first person over whose grave water was poured ?

A 2: Water is sprinkled over a grave immediately after burial to allow the earth to become compact and solid. Al-Shafi`y mentioned in his Musnad, as did Sa`id ibn Mansur and Al-Bayhaqy in a Hadith Mursal (a Hadith with no Companion of the Prophet in the chain of narration) that the Prophet (peace be upon him) sprinkled water over the grave of his son Ibrahim and put pebbles on it. It was related by Sa`id ibn Mansur that sprinkling water over graves was practiced during the lifetime of Allah's Messenger (peace be upon him). As regards its permissibility, it was maintained by the three Imams (initiators of Schools of Jurisprudence), Abu Hanifah, Al-Shafi`y and Ahmad, and this is also the opinion of other scholars.May Allah grant us success. May peace be upon our Prophet Muhammad, his family and Companions!