That the Messenger of Allah (ﷺ) said: "War is deceit."

There are narrations on this topic from 'Ali, Zaid bin Thabit, 'Aishah, Ibn 'Abbas, Abu Hurairah, Asma' bint Yazid bin As-Sakan, Ka'b bin Malik and Anas bin Malik. This Hadith is Hasan Sahih.

Jami` at-Tirmidhi Book 23, Hadith 6