St. John Maximovich of Shanghai and San Francisco

Adam and Eve, before their Fall, were in full accord and of common spirit with one another at all times. Having sinned, alienation was immediately sensed. Justifying himself before God, Adam blamed Eve. Their sin divided them and continues to divide all of mankind. Emancipated from sin, we approach God, and, filled with His grace, we sense our unity with the rest of mankind. Such unity is very imperfect and lacking, since in each person some portion of sin remains. The closer we approach God, the closer we approach each other, just as the closer rays of light are to each other, the closer they are to the Sun. In the coming Kingdom of God there will be unity, mutual love and concord. The Holy Trinity remains eternally unchanging, all-perfect, united in essence and indivisible.

Source: St. John Maximovich of Shanghai and San Francisco  -  "On the Holy Pentecost", quoted in Orthodox Church Quotes, http://www.orthodoxchurchquotes.com/tag/unity/