My daughter was like this when she was 6 or 7.

Hi, once I was visiting museum with her, she stole 10 mini flash lights of book shape (very cute and lovely item). She said she wanted to bring to friends as gifts. I was very shocked. I explained to her the consequences and plead to her that she should never do it again. she never did again, and she conducts her daily social life very gracefully.  Now she is watching me all the time, for instance, not to steal a tea bag or apple in hotel breakfast. 

You need express your understanding of your son's good intention but also need explain to him the bad consequences of stealing that will ruin a person's whole life.