When your kid reaches the age of 4 years, he starts getting influenced by the people around him and mostly his friends. At this age, he wants to do every possible thing to please his friends using his books, toys, food, etc. as he wants his friends to like him.
What you need to know:
As a parent, you need to assist him in forming relationships with people around but you also need to see what kind of friends he is trying to please or make. If he is not gelling with the right kind of friends then help him find the ones who will be an asset for him and he can learn from their good habits.