הלכה על שבת 61:6

The commandment of love of Israel: To love [with] love of the soul each one of Israel - meaning to say that we have compassion for an Israelite and for his money, [just] like a person has compassion for himself and for his [own] money; as it stated (Leviticus 19:18), "you shall love your neighbor as yourself." And they, may their memory be blessed, said (Shabbat 31a), "What is hateful to you, do not do to your fellow." And they said in Sifra, Kedoshim, Chapter 4:12, "Rabbi Akiva said, 'This is a great principle in the Torah'" - meaning to say that many commandments are dependent upon it. As one that loves his fellow like himself will not steal his money, have adultery with his wife, cheat his money from him nor hurt him from any angle. And so [too,] are there several other commandments dependent on this - the thing is well-known [revealed] to all who have intellect.