The ruling on sprinkling graves with water and planting vegetation on them

Question : The questioner says here, in a letter from his location, that he wants to present it before its ruling, which is the objection raised by some people regarding the practice of sprinkling graves with water or planting summer vegetation on them.

Answer : Yes, my brother, if the weather is hot and you sprinkle the grave with what drives away the heat from the top of the grave, this is kindness to the person in the grave. Do you agree with this?
Is water not cooling? Does water not, when you sprinkle it on the clay, go down until it reaches the dead person? Well, this is a benefit. And you know that you are in a hot region in Jeddah; if you were with us there in al-Qasim, it would be a bit cooler, and we would not do this. The garden also delights the one who looks at it, as Allah the Exalted said in the surah: and We caused to grow therein from every kind of beautiful fruit So planting, my brother 'Ali, delights a person and refreshes him. And this dead person, if he knew that there was planting on the top of his grave, would be happy, would he not? Answer him: No, or yes, there is nothing that makes him happy.
We say that this is an act of religious innovation (bid'ah) and an act of foolishness, to sprinkle water on a grave. And if the grave is sealed with cement, this water may reach the cement, wet it, and cause it to collapse on the dead person; it collapses on the dead person.
As for placing trees, the one who places a tree on the grave of a dead person is following the example of the Messenger of Allah (peace and blessings be upon him) in the story of two men who testified to the punishment of a dead person. This is one of the greatest forms of undutifulness to parents. Did the Messenger of Allah (peace and blessings be upon him) place a fresh branch on every grave? Never. Or did he place any trees or branches on them? No, he did not do this. He placed this on two graves that were being punished and said, "Perhaps it will lighten the punishment for them as long as they do not dry out." So if you place a fresh branch on the grave of your father or your mother or your brother, if you place a fresh branch on his grave, it is as if you are saying, "Bear witness, O servants of Allah, that this man is being punished, and that I have placed this branch on his grave." And this is undutifulness. If someone came to you and said, "Come, your father in this grave is being punished," would you be pleased with this or not? You would not be pleased. So placing a branch on any grave is considered an innovation from the perspective of following the Messenger (may Allah praise and bless him), because the Messenger did not place them on every grave. And it is considered undutifulness and severing ties with regard to the dead person, because this entails that you are testifying that he is being punished.