One should recite the following Duaa when bidding someone farewell at the time he departs on a journey:
أَستَودِعُ اللهَ دِينَكَ وَأَمَانَتَكَ وَخَوَاتِيمَ عَمَلِكَ
I place your deen, your trust (wife, children and subordinates) and your final actions (at the time of death) in the care and trust of Allah Ta’ala
عن سالم أن ابن عمر كان يقول للرجل إذا أراد سفرا ادن مني أودعك كما كان رسول الله صلى الله عليه و سلم يودعنا فيقول أستودع الله دينك وأمانتك وخواتيم عملك (ترمذي رقم 3443)
Hazrat Saalim (Rahmatullahi Alaihi) reports that Hazrat ibn Umar (Radhiyallahu Anhuma) would address a person embarking on a journey with the following words: “Come close to me so that I may bid you farewell in the manner that Rasulullah (Sallallahu Alaihi Wasallam) would bid us farewell (when we would depart on a journey). He would then say:
أَستَودِعُ اللهَ دِينَكَ وَأَمَانَتَكَ وَخَوَاتِيمَ عَمَلِكَ
Source: Ihyaauddeen.co.za