You never answered the question, other than with a reference to the OT. Are there any other references to loving your neighbor in OLDER texts? It's a simple question actually and hopefully someone can provide an answer for us.
The idea seems to have gained currency during the Axial Age in all the major cultures of the time.
The Mahabharata (Hindu) says, "That man who regards all creatures as his own self, and behaves towards them as towards his own self, laying aside the rod of chastisement and completely subjugating his wrath, succeeds in attaining to happiness."
Confucius says, "Never impose on others what you would not choose for yourself."
Isocrates says, "Do not do to others what would anger you if done to you by others."
It's sometimes claimed that the originality of Jesus was in formulating the Golden Rule in positive terms, but Sextos the Pythagorean preceded him in that, saying, "What you wish your neighbors to be to you, such be also to them."
The Acaranga Sutra (Jain) has perhaps the strongest version, extending the rule beyond humans: "Nothing which breathes, which exists, which lives, or which has essence or potential of life, should be destroyed or ruled over, or subjugated, or harmed, or denied of its essence or potential."