IT IS MUSTAḤABB to congratulate a person to whom a child is born. Our [Shāfi‘ī] colleagues say it is mustaḥabb to congratulate him in the way that has been reported from al-Ḥusayn 
. He said that he taught a man to say: “May Allah bless you in what has been granted to you, and may you thank the Giver. May he reach maturity and may you be granted kind treatment by him.”
. He said that he taught a man to say: “May Allah bless you in what has been granted to you, and may you thank the Giver. May he reach maturity and may you be granted kind treatment by him.”
Bāraka-llāhu laka fi-l-mawhūbi lak, wa shakarta-l-Wāhib, wa balagha ashuddah, wa ruziqta birrah.
It is mustaḥabb for someone who has been congratulated to reply by saying: “May Allah bless you and send blessings upon you,” and “May Allah grant you a goodly reward,” and “May Allah grant you the same” or “May Allah confer an abundant reward upon you” and suchlike.
Bāraka-llāhu laka wa bāraka ‘alayk; or, Jazāka-llāhu khayrā; or, Razaqaka-llāhu mithlah; or, Ajzala-llāhu thawābak.