Do not call every sentence without an explicit noun passive.
● نَصَرَ — He helped. The hidden pronoun is the doer, so it is active.
● نَصَرُوا — They helped. The wāw is the doer, so it is active.
● نُصِرَ مَحْمُودٌ — Mahmood was helped. An explicit noun follows as نائب الفاعل, so the verb stays singular.
● نُصِرُوا — They were helped. The نائب الفاعل is encoded in the verb, so the verb is conjugated.