What is the ruling on seeking aid from a deceased person, knowing that benefit and harm are in the hand of Allah alone, and that neither the living nor the dead possess benefit or harm except by the permission of Allah?

If seeking aid from other than Allah in a matter that none but Allah can accomplish, it is major polytheism (shirk (definition) akbar) that expels one from the fold of Islam, regardless of whether the one from whom aid is sought is alive or dead. However, if it is in a matter that humans are capable of, such as a drowning person seeking aid from someone present to rescue him, it is permissible if the one from whom aid is sought is alive. As for the dead, they are incapable of any such thing. The statement, "The living and the dead do not benefit except by Allah's permission," is a refutable misconception, because the discussion is about human capability, not Allah's capability. It is not permissible to seek aid from stones and trees under the pretext that they do not benefit except by Allah's permission. We have not been permitted to seek aid from the dead or the absent, and the prohibition is general against invoking and asking other than Allah. Asking the living for what they are capable of is specifically exempted by evidence.