SB 10.10.14
yatha kantaka-viddhango
jantor necchati tam vyatham
jiva-samyam gato lingair
na tathaviddha-kantakah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
By seeing their faces, one whose body has been pricked by pins can understand the pain of others who are pinpricked. Realizing that this pain is the same for everyone, he does not want others to suffer in this way. But one who has never been pricked by pins cannot understand this pain.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
There is a saying, “The happiness of wealth is enjoyable by a person who has tasted the distress of poverty.” There is also another common saying, vandhya ki bujhibe prasava-vedana: “A woman who has not given birth to a child cannot understand the pain of childbirth.” Unless one comes to the platform of actual experience, one cannot realize what is pain and what is happiness in this material world. The laws of nature act accordingly. If one has killed an animal, one must himself be killed by that same animal. This is called mamsa. Mam means “me,” and sa means “he.” As I am eating an animal, that animal will have the opportunity to eat me. In every state, therefore, it is ordinarily the custom that if a person commits murder he is hanged.