Sayyiduna Ka'b bin Malik (may Allah be pleased with him) says: Rarely did the Prophet (peace and blessings be upon him) intend a campaign without using tawriyah (concealing his true destination). When the occasion of the Battle of Tabuk came, the Messenger of Allah (peace and blessings be upon him) faced intense heat, a long journey and a numerous enemy. He (peace and blessings be upon him) made the matter clear to the Muslims so that they could prepare for their enemy, and informed them of the true direction.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18450