Sunan Abi Dawud 2597
سنن أبي داود#2597SahihNarrated A man who heard the Prophet: Al-Muhallab ibn AbuSufrah said: A man who heard the Prophet (ﷺ) say: If the enemy attacks you at night, let your war cry be Ha-Mim. They will not be helped
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Zubair Ali ZaiSahih
In-book reference: 15:121