Musannaf Ibn Abi Shaybah

Hazrat Abdur Rahman bin Ka'b bin Malik narrates from his father that it was the habit of the Messenger of Allah, peace and blessings be upon him, that when he intended to undertake a military expedition, he would use ambiguous language with others (about his destination), until the expedition of Tabuk occurred. The Messenger of Allah, peace and blessings be upon him, undertook the journey to Tabuk in intense heat, and in this journey, he had to travel a long distance. Therefore, the Messenger of Allah, peace and blessings be upon him, clarified the matter (i.e., the expedition) to the Muslims and informed them about it so that the people could make preparations suitable to the enemy's equipment. And the direction in which the Messenger of Allah, peace and blessings be upon him, intended to go, he also informed the companions about it.