What is the beginning of the Messenger of Allah, may Allah bless him and grant him peace?

If the question is about the beginning of the Prophet’s mission (peace and blessings be upon him), then Ahmad, Ibn Hibban, and others narrated that the Prophet (peace and blessings be upon him) said: “I am inscribed with Allah as the Seal of the Prophets, even while Adam was still intertwined in his clay.” He also informed about the beginning of his affair, saying: “I am the prayer of my father Ibrahim, the glad tidings of Jesus, and the vision of my mother, who saw, when she gave birth to me, a light emanating from her by which the palaces of Sham (Syria) were illuminated.”