The Prophet ﷺ saw travellers off by entrusting their faith and deeds to Allah (SWT) and praying for taqwa, forgiveness and ease, and the traveller leaves those at home in the care of Allah (SWT), whose trusts are never lost.
Astawdi'u-llaha dinaka, wa amanataka, wa khawatima 'amalik
“I leave your faith, your trustworthiness and the final outcome of your deeds in the care of Allah.”
Said by those staying behind to the one who is travelling, as the Prophet ﷺ used to say when seeing people off.
Astawdi'ukumu-llaha-lladhi la tadi'u wada'i'uh
“I leave you in the care of Allah, whose trusts are never lost.”
Said by the one setting out, to the family and friends staying behind. Ibn Majah's wording addresses one person: Astawdi'uka-llah.
Zawwadaka-llahu-t-taqwa, wa ghafara dhanbak, wa yassara laka-l-khayra haythu ma kunt
“May Allah give you taqwa as your provision, forgive your sins, and make good easy for you wherever you are.”
Taqwa is mindful awareness of Allah (SWT) that keeps a person obedient to Him and away from what He has forbidden.