Mukhtasar Bukhari (Abridged) 385 — If travelers are many, give adhan

Narrated by Sayyiduna Ibn Umar (may Allah be pleased with them both): The Messenger of Allah (peace and blessings of Allah be upon him) used to instruct the mu’adhdhin, after the adhan, to say: "Pray in your places" (and do not come for the congregation), and this was done on cold or rainy nights (when) on a journey.