When a parent spanks a child for hitting another child, the parent is the behavior for the child, which will affect the effectiveness of the punishment?

The answer to this question is modelling the exact behavior.
When a child saw his/her parents hits another child, that child will indirectly receive approval/acknowledgement to justify that certain behavior.
This will most liekly lead to the child thinking that it's okay to mimic the behavior of his/her parents