Musnad Abu Ya'la al-Mawsili 161:38

Amr ibn Husayn narrated to us, Yahya ibn al-Ala narrated to us, from Suhayl, from his father, from Abu Hurayrah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "When one of you intends a journey, let him bid farewell to his brothers, for they will add to his supplication with their own supplication, goodness."