What is the ruling on invoking blessings upon the Messenger (peace be upon him) with the phrase, "May God's prayers and peace be upon you, O Beacon of Guidance," or "May God's prayers and peace be upon you, O Messenger"?

If the intended prayer with this wording is outside of regular prayers (salat), then it is permissible. If it is within the regular prayers, we hope that it is sufficient, as jurists have stated that praying upon the Prophet (peace be upon him) with any wording is sufficient. The best wording for it, however, is that which is mentioned in the hadith: "O Allah, send prayers upon Muhammad and upon the family of Muhammad, as You sent prayers upon Ibrahim and upon the family of Ibrahim. And send blessings upon Muhammad and upon the family of Muhammad, as You sent blessings upon Ibrahim and upon the family of Ibrahim among the nations. Indeed, You are Praiseworthy and Glorious."