Whenever the Messenger of Allah ﷺ intended to launch a military expedition, he would almost always disguise his true destination by hinting at another, until the expedition of Tabuk came. The Messenger of Allah ﷺ undertook this expedition in intense heat, facing a long journey through barren wilderness and confronting a large enemy force. So he made the situation clear to the Muslims so they could prepare adequately to face their enemy, and he informed them of the destination he intended.
و حدثني أحمد بن محمد أخبرنا عبد الله أخبرنا يونس عن الزهري قال أخبرني عبد الرحمن بن عبد الله بن كعب بن مالك قال سمعت
كان رسول الله ﷺ قلما يريد غزوة يغزوها إلا ورى بغيرها حتى كانت غزوة تبوك فغزاها رسول الله ﷺ في حر شديد واستقبل سفرا بعيدا ومفازا واستقبل غزو عدو كثير فجلى للمسلمين أمرهم ليتأهبوا أهبة عدوهم وأخبرهم بوجهه الذي يريد
Bukhari narrated the hadith of Kaab's repentance through sahih chains, from Yunus, Aqeel, and Ishaq bin Rashid, from Zuhri, from Abdul-Rahman bin Abdullah bin Kaab, from his father, from Kaab. This is the correct version.He also narrated it from Ahmad bin Muhammad, from Ibn Mubarak, from Yunus, from Zuhri, from Abdul-Rahman bin Kaab, from Kaab, as a mursal narration.Suwayd narrated it from Ibn Mubarak as a connected chain, similar to what Ibn Wahb and Layth reported from Yunus.Muslim narrated it through sahih chains from Yunus, Aqeel, and the nephew of Zuhri, from Zuhri, in accordance with the correct version. And also from Salama, from Ibn Ayman, from Maqil, from Zuhri, from Abdul-Rahman, from his uncle Ubaydullah bin Kaab, from Kaab.He said, "Salih bin Abu Akhdar corroborated Maqil regarding Ubaydullah bin Kaab, but both of them failed to preserve it accurately, and the first version is the correct one."