If the context makes the affected singular masculine person clear, ضُرِبَ can stand alone, with an implicit «هُوَ» serving as the passive subject.
Do not confuse the omitted agent with the implicit passive-subject pronoun. One is the unmentioned actor; the other points to the person undergoing the action.
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Mafʿūl Mā Lam Yusamma Fāʿiluhu — The Passive Subject
If the context makes the affected singular masculine person clear, ضُرِبَ can stand alone, with an implicit «هُوَ» serving as the passive subject.
Do not confuse the omitted agent with the implicit passive-subject pronoun. One is the unmentioned actor; the other points to the person undergoing the action.