Musannaf Ibn Abi Shayba 21:489

Yahya ibn Sa'id narrated to us, from Ibn 'Ajlan, who said: 'Awn ibn 'Abdullah narrated to me that a man came to Ibn Mas'ud and said, "I intend to travel, so advise me." He said, "When you set out, say: 'In the name of Allah (Bismillah), Allah is sufficient for me (Hasbi Allah), and I have relied upon Allah (Tawakkaltu 'ala Allah).' For when you say 'In the name of Allah,' the angel says, 'You have been guided.' When you say 'Allah is sufficient for me,' the angel says, 'You have been protected.' And when you say 'I have relied upon Allah,' the angel says, 'You have been sufficed.'"