The Rambam writes (Hilchot De'ot 6:3):
"It is a mitzva for every Jew to love every other Jew like his own self... Therefore a person must praise his fellow Jew and be careful with his property the same way he is careful with his own property and desires to be treated respectfully. Whoever seeks honor through his neighbor's shame has no portion in the World-to-Come..."

Sefer HaChinuch writes (Mitzva 243 [219]):
"It is a mitzva to love every Jew deeply."

Our Sages said (Eliyahu Rabbah 28):
So said G-d to Israel: "My children! Have I failed to give you anything? What do I ask of you? Only that you love, respect and revere one another, and that you avoid all sin, theft and unseemly behavior."

Our Sages also said (Avot 2:10):
"Let your friend's honor be as dear to you as your own."

"Do not stand idly by the blood of your neighbor. I am the L-rd." Vayikra (Leviticus) 19:16

Of this King Solomon said (Proverbs 24:10-12):
If you faint in the day of adversity, your srength is small indeed. If you forbear to rescue those taken to be killed and those ready to be slain, if you say, "We did not know," does He Who ponders the heart not consider it? And He Who keeps your soul, does He not know it? Shall He not render to every man according to his work?

Similarly, King Solomon said (Proverbs 21:13):
"He who stops his ears at the cry of the poor shall also cry himself but shall not be answered."

Our Sages said (Shavuot 39a):
"All of Israel (the Jewish People) are guarantors for one another."

When Rav Eliezer became ill (Berachot 28b):
His students came to visit him, and they said, "Master! Teach us how to live so we can merit the World-to-Come!" He replied, "Be careful to treat your fellow man with respect."