The Inclusive Golden Rule

Many Gedolim (great scholars) has instructed us to follow the custom of the Ari"zal by stating prior to prayer: "Hareini mekabel 'alai mitzvas 'asei shel ve-ahavta le-re'akha kamocha" - Behold, I accept upon myself the positive commandment to 'love your fellow as yourself' (Leviticus 19:18). According to Rabbi Akiva, one of the foremost Talmudic sages, this is the great principle in the Torah ("K'lal gadol ba-Torah").

While many people render the word 're'akh' here as 'your fellow Jew' (according to its context), this great principle can always be broaden to its fullest expression to include the whole humanity.

There is famous story of Rabbi Hillel, who lived in the 1st century B.C.E.

A gentile who wants to convert asked Hillel to teach him the entire Torah while standing on one foot. Hillel replied, “What is hateful to yourself, do not do to your fellow man. That is the whole of Torah and the rest is but commentary. Go and study it.” (Babylonian Talmud, Shabbat 31a)

To include all men, the same Hillel used the term "beriot" (creatures) when inculcating the teaching of love: "Love the fellow-creatures" (Abot i. 12). Hatred of fellow-creatures ("sinat ha-beriyot") is similarly declared by R. Joshua b. Hananiah to be one of the three things that drive man out of the world (Abot ii. 16). 

The term "neighbor" has at all times been thus understood by Jewish teachers. In Tanna debe Eliyahu R. xv. it is said: "Blessed be the Lord who is impartial toward all. He says: 'Thou shalt not defraud thy neighbor. Thy neighbor is like thy brother, and thy brother is like thy neighbor.'" Likewise in xxviii.: "Thou shalt love the Lord thy God"; that is, thou shalt make the name of God beloved to the creatures by a righteous conduct toward Gentiles as well as Jews (compare Sifre, Deut. 32). Aaron b. Abraham ibn Ḥayyim of the sixteenth century, in his commentary to Sifre, l.c.; Ḥayyim Vital, the cabalist, in his "Sha'are Ḳedushah," i. 5; and Moses Ḥagis of the eighteenth century, in his work on the 613 commandments, while commenting on Deut. xxiii. 7, teach alike that the law of love of the neighbor includes the non-Israelite as well as the Israelite.

Not surprisingly, Israel's postal service quoted from this commandment when it commemorated the Universal Declaration of Human Rights on a 1958 postage stamp.

Source: Jewish Encylopedia on Brotherly Love