What is the ruling on saying: "I have believed in Allah, I have relied upon Allah, I have held fast to Allah, and I have sought refuge with the Messenger of Allah, may Allah's peace and blessings be upon him"?

The statement "I believe in Allah, and I rely upon Allah, and I hold fast to Allah" is permissible, as it describes the state of every believer. However, the statement "and I seek refuge with the Messenger of Allah, may Allah bless him and grant him peace" is an abominable statement, because seeking refuge with the Prophet after his death is not permissible and is major polytheism (shirk akbar). As for seeking refuge with him during his lifetime regarding matters within his capability, that is permissible. It is obligatory to advise anyone who says this and to explain that it is polytheism.