The Sefer Yesod V’Shoresh HaAvoda ( first gate, chapter 8) explains why Ahavat Yisrae l is so important. He says , “ It is well-known among human beings that if a person is suffering, and sees that other people feel bad with him, there a certain amount of comfort in that. But if he sees that no one cares about him , and he ’s just being forgotten, then his pain is even deeper . ” He qu otes a pas uk from Shemuel א (22,8) where Shaul Hamelech says, וְאֵין־חֹלֶ֥ה מִכֶּ֛ם עָלַ֖י No one is getting sick over me Nobody cares what is going on with me. The Sefer continues, It’s well known that God feels bad when a person is in pain , as it says, “ W hen a person is in pain , God H imself says, “ My head hurts, My arm hurts ,” and that is the way God feels over a wicked person; so surely when a righteous person suffers. If that’s the case, when a person is feeling bad because his friend is in pain ( which is VeAhavta LeReecha Kamocha/ loving your friend like you love yourself ), he is removing part of God‘s pain. God is that F ather who is suffering , because His child is suffering. And so when I also feel bad, I make it a little easier, so to say, for God, because someone else is feeling His pain - that gives Hashem a good feeling. This works for the positive as well. W hen a person has a new child or other success in his life, and others are happy, as if that child or success w ere theirs , they too are fulfilling VeAhavta LeRe’echa Kamocha. They are happ y because God is happy that there are more children being born and more Mitzvot being done . When we are happy for our friend s’ happiness, we are giving Hashem th at feeling that we are also happy with His happiness. In his words, “ With this happiness over your friend ’s good fortune, you are serving God a great and unbelievable service, to no end. ” And the opposite is true as well. This is a fascinating concept. When we are happy with our friends happiness, and when we are in pain when he is in pain, we are actually giving a good feeling to Hashem, and that is the ultimate purpose that we are here for - To give our C reator a good feeling. That is what happens when He sees that we are feeling for our fellow man, when we are feeling God’s pain , when our fellow man is not in the right place. Have a wonderful day.