Reb Chaim Shmulevitz explains that the common denominator among these four is that they do not feel someone else’s pain and that they cannot provide benefit for others.
A poor person is considered as dead not because he is lacking himself, but rather, it is because he cannot give to others.
A blind person cannot see others and therefore, he is unable to perceive their pain or suffering. He cannot join in his tribulation.
A metzora is banished from the camp and therefore, he is unable to offer assistance to others.
One who does not have children to nurture is lacking the ability to provide benefit to those that are dear and close to him. It is a natural instinct for a person to desire to give whatever he has to his children.
Only a life where one can share with others is worth living. Read more!