Sayyiduna Salamah bin Akwa’ (may Allah be pleased with him) said: I confronted a man and killed him, so the Messenger of Allah (peace and blessings be upon him) gave me his belongings and possessions. And on that day, our code word with Sayyiduna Khalid bin al-Walid (may Allah be pleased with him) was “Umt,” meaning “kill (him).”
Hadith Referenceسنن دارمي / من كتاب السير / 2488
Hadith Gradingتحقیق (حسین سلیم أسد الدارانی):إسناده صحيح والحديث متفق عليه، [مكتبه الشامله نمبر: 2495]
Hadith Takhrijاس روایت کی سند صحیح ہے۔ دیکھئے: [أبوداؤد 2596] ، [ابن حبان 4839]
Brief Explanation
(Commentary on Hadith 2487)
In this hadith, the meaning of "shi'ar" is that sign or word by which soldiers recognize one another, so that there is no confusion, and a brother does not kill his brother.
At the time of a night raid, such a situation can arise; therefore, a code word is established, as in the aforementioned hadith where the word «أَمِتْ» is mentioned.
In other ahadith, the words «حم لا ينصرون» and other such terms are found.