´Abu Hurairah narrated that:` When supplicating for the newlywed, the Prophet would say: (Barak Allahu laka wa baraka alaik, wa jama'a bainakuma fi khair.) "May Allah bless you and send blessings upon you, and bring goodness between you."
Hadith Referenceسنن ترمذي / كتاب النكاح عن رسول الله صلى الله عليه وسلم / 1091
Narrated Abu Hurairah: When the Prophet ﷺ congratulated a man on his marriage, he said: May Allah bless for you, and may He bless on you, and combine both of you in good (works).
Shaykh Umar Farooq Saeedi
Benefits and Issues: On such occasions of happiness, one should offer pure and Sunnah supplications as congratulations, which encompass all apparent and hidden meanings of affection, love, and increase.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 2130