There are a number of traits that distinguish human beings from other forms of life. Man can do for others even at the cost of his own comfort. With the exception of pets who may adopt human traits, animals are incapable of sacrificing themselves for the benefit of others. No tiger has ever left over a carcass so that a hungry jackal might have food. All living things act in their own interest.
Man can be unique in one of two ways.
He can sacrifice his personal comfort in order to help others. He can alter his character so that other people's discomforts become his own. Even if one does not achieve the latter, the minimum criterion of humanity is to be able to set aside one's own comfort for the benefit of others. This is the message of the verse cited, said the Rebbe of Rizhin. One can be considered to be a person only if one can sacrifice of himself.