To someone who says "May Allah bless you"

Wafīka bārakallāh.

And may Allah bless you.

[ Ibn As-Sunni, p. 138, (no. 278). See also Ibn Al-Qayyim, Al-Wdbil As-Sayyib, p. 304, with checking by Basheer Muhammad ?Uyoon. Hisn al-Muslim 204 ]