An object is not always an explicit noun. It may be an attached pronoun.
ضَرَبَ حَامِدٌ مَحْمُودًا — Hamid hit Mahmood.
ضَرَبَهُ حَامِدٌ — Hamid hit him.
In the second sentence, هُ means “him.” It is attached directly to the verb and is the object. The explicit subject حَامِدٌ follows the verb with its attached object.