What is said in the marriage sermon? May Allah reward you with all good.

It is best to commence the marriage contract with the Khutbat al-Hajah (Sermon of Need), as the Prophet, peace and blessings be upon him, did. It is: "Indeed, all praise is due to Allah; we praise Him, we seek His help, and we seek His forgiveness. We seek refuge in Allah from the evils of our souls and from the bad consequences of our deeds. Whomsoever Allah guides, no one can misguide, and whomsoever Allah misguides, no one can guide. I bear witness that there is no god worthy of worship except Allah, alone, without any partner, and I bear witness that Muhammad is His servant and His messenger." Then, the verses of piety from Surahs Al Imran, An-Nisa, and Al-Ahzab are recited, followed by: "To proceed: The best of speech is the Book of Allah, and the best of guidance is the guidance of Muhammad. The worst of affairs are their innovations, and every innovation is a bid'ah (heresy), and every bid'ah is misguidance." There is no harm in adding some verses, hadiths, and admonitions.