What is the ruling on saying "Sayyid al-Wujud" (Master of Existence) for the Prophet, peace and blessings be upon him, and is it permissible to advise the imam of the mosque who uses this expression?

It is not permissible to describe the Prophet, peace and blessings be upon him, as the 'Master of Existence,' for this absolute mastery belongs to Allah alone. As for the Prophet, peace and blessings be upon him, he is, by consensus, the master of the children of Adam and the best of Allah's creation, as stated in the Hadith: "I am the master of the children of Adam on the Day of Resurrection." It is forbidden to praise with falsehood and fabricated narrations, for the Prophet, peace and blessings be upon him, said: "Do not exaggerate in praising me as the Christians exaggerated in praising the son of Mary, for I am only His slave, so say: 'Allah's slave and His Messenger.'"