שלי שלי ושלך שלך, זו מדה בינונית, ויש אומרים זו מדת סדום (אבות ה:י)

There are two ways of thinking. Someone thinks “שלי” – Hashem gave me my belongings, and I’m not jealous of my friends.  Therefore, “שלך שלך” – your is yours – without any feelings of jealousy.  A second thought can be “שלי שלי” – everything I possess is from my prowess, and therefore I will not share with another “שלך שלך” – these are the two opinions of the Mishna.  The first one: Is a median characteristic since he is not jealous of what his friend possesses; the second one is characteristic of the Sodomite since he does not even want to share with others.