YOM KIPPUR: FORGIVING SIN BETWEEN MAN AND YHVH

In Mishneh Torah Hilchos Teshuvah 2:9, Rambam (Moses Maimonides) explains that Teshuvah and Yom Kippur only atones for sins between man and the God of Israel but sins between one man and another are not forgiven until one gives the other his due and appeases him. This thought is also found in Talmud Yoma 85b.