Aaishah (radhi-yAllahu 'anhaa) said: The Messenger of Allah (sal-Allahu 'alayhe wa sallam) got a sheep as a gift. He told his servant to give it away. Every time the servant came back, Aaishah asked: "What did people say?" He answered: "They made this dua:
بَارَكَ اللَّهُ فِيكُمْ
Transliteration
BaarakAllahu feekum
Translation
May Allah bless you all
Aaishah would then say:
وَفِيهِمْ بَارَكَ اللَّهُ
Transliteration
wa feehim baarakAllah
Translation
And may Allah bless them.
وَفِيكَ بَارَكَ اللَّهُ
Transliteration
Wa feeka baarakAllah
Translation
And May Allah bless you.
Note
So we return the dua in the same way, hoping for the same reward.
Hadith About Sending Salat to Get Forgiveness