´Narrated Ibn 'Asim Al-Muzani:` From his father and he was a Companion who said: "When the Messenger of Allah (ﷺ) dispatched any army or battalion, he would say to them: 'If you see a Masjid, or hear someone calling the Adhan, then do not kill anyone.'"
Related hadith on this topic
Explanation & Benefits
Shaykh Dr. Abdur Rahman Freywai
Explanation:
1:
That is, when any sign or symbol of Islam becomes apparent, then do not attack until the distinction between believer and disbeliever becomes clear.
Note:
(In the chain of narration, "Abdul Malik bin Nufal" is weak in hadith, and "Ibn ‘Isam" is an unknown narrator.)
Source: Sunan al-Tirmidhi – Majlis ‘Ilmi Dar al-Da‘wah, New Delhi Edition, Page: 1549