What is the ruling on saying: "Intercession, O Messenger of Allah" when commencing the prayer, and is it permissible to pray behind someone who says it?

There are two types of requesting supplication or intercession from the Prophet, peace and blessings be upon him. The first is directing acts of worship to him, such as prostration, vows, and supplication. This is major shirk (definition) (polytheism) by the consensus of scholars. The second is requesting supplication or intercession from him without directing any worship to him. Scholars have differed on this. Some have held that it is an innovation (bid'ah), reprehensible, and a means leading to shirk. Others have held that it is major shirk. However, a ruling of disbelief (kufr) on a statement does not mean that everyone who utters it is deemed an apostate, for they may be excused due to ignorance or misinterpretation, just as one who lives in an environment where disbelief is practiced is excused due to ignorance, or if scholars have approved it there. We do not declare the imams who err in these matters to be disbelievers. Rather, we permit praying behind them and advise them by clarifying that what they say is an innovation and a means to shirk, or major shirk according to many scholars.