Authentic Supplication Number 190.

It is reported of the Prophet  that he said: Whoever wants to go on a journey, then let him say to those whom he leaves behind: 'Astawdi`ukumul-laha 'allathee la tadhee`u wada'i`uhu (203).

Footnotes.
(203) I entrust you unto Allah, Whose trusts are not lost.

Reporters.
Al-Albani said it was of comely ascription and that it was reported by Ibn Majah, and An-Nisa'ee in his [`Aml al-yaum wal-lailah]. He said that also Ibn As-Sunni, and Ahmad reported it, and that Al-Hafith said it was comely. Al-Albani included this hadeeth in The Authentic of Good Sayings as #133.