أَسْتَوْدِعُكَ اللَّهَ الَّذِيْ لَا تَضِيْعُ وَدَائِعُهُ

Astawdi'ukAllahal-ladhee laa tadhee'u wadaa'i'uhu

I leave you in the care of Allah, as nothing is lost that is in His care. The Messenger of Allah (ﷺ) gave me a send-off and said: (The dua is mentioned above). So, musaafir should say this dua to the farewell giver.But Musaafir and farewell giver both can supplicate this dua for each other.

Reference: Sahih (Albani). Ibn Majah: 2825