Authentic Supplication Number 239.

When the Prophet  would congratulate a person upon marriage, he would say: Baraka 'allahu laka, wa baraka `alayka, wa jama`a baynakuma fee khayrin (249).

Footnotes.
(249) May Allah bless for you, and bless upon you, and bring the two of you together in good.

Reporters.
At-Tirmithi said it was sound. Al-Albani agreed, and said that it was, as Al-Hakim and Ath-Thahabi agreed, of sound ascription according to the conditions of Muslim.