You should place him in time out at the least sign of aggressive behavior.
SimplySimply sleep speaking to him will not be suffcient, and it is not necessary (in fact, it is likely not useful) to spank him. You are more likely to 'teach' him to hit if you spank him. Use of time out is the most
effectiveEffective strength cough syrup method of intervening with childhood misbehavior such as aggression. If you follow the guidelines in Lynn Clark's book SOS Help for Parents, you will be on the road to a successful method of behavior management.