Whenever someone got married, the Prophet ﷺ would offer congratulations by saying, "May Allah bless you, may He shower His blessings upon you, and may He unite you both in goodness."
حدثنا قتيبة بن سعيد حدثنا عبد العزيز يعني ابن محمد عن سهيل عن أبيه
أن النبي ﷺ كان إذا رفأ الإنسان إذا تزوج قال بارك الله لك وبارك عليك وجمع بينكما في خير
[Its chain is sahih] Tirmidhi narrated it, Nikah, chapter on what is said to one who marries, hadith no. 1091, from Qutayba with this wording, and he said, "Hasan sahih." Ibn Majah also narrated it, hadith no. 1905, and Ibn Hibban graded it sahih, hadith no. 1284, as did Hakim, according to the criterion of Muslim, 2/183, and Dhahabi agreed with him.