The one embarking on a journey should recite the following Duaa when bidding farewell to the people he is leaving behind
أَسْتَوْدِعُكُمُ اللَّهَ الَّذِي لَا تَضِيعُ وَدَائِعُهُ
I place all of you in the care (and trust) of Allah Ta’ala, (in whose care) trusts are never destroyed
عن موسى بن وردان، قال: أتيت أبا هريرة أودعه لسفر أردته، فقال أبو هريرة رضي الله عنه: ألا أعلمك يا ابن أخي شيئا علمنيه رسول الله صلى الله عليه وسلم أقوله عند الوداع؟ قلت: بلى. قال: قل: أستودعكم الله الذي لا تضيع ودائعه (عمل اليوم والليلة لابن السني رقم 505)
Hazrat Moosa bin Wardaan (rahimahullah) relates: “On one occasion I came to Hazrat Abu Hurayrah (radhiyallahu ‘anhu) to bid farewell to him as I intended to undertake a journey. Hazrat Abu Hurayrah (radhiyallahu ‘anhu) said, ‘O my nephew, should I not teach you something that Rasulullah (Sallallahu ‘alaihi wasallam) taught me to recite at the time of bidding farewell?’ I said, ‘Yes, do teach me.’ Hazrat Abu Hurayrah (radhiyallahu ‘anhu) said, ‘Recite the following duaa (to those whom you bid farewell):'”
أَسْتَوْدِعُكُمُ اللَّهَ الَّذِي لَا تَضِيعُ وَدَائِعُهُ
Source: Ihyaauddeen.co.za