"Agape characterizes God and what He manifested in the gift of His Son. It is more than mutual affection; it expresses unselfish esteem of the object loved. Christ’s love for us is undeserved and without thought of return. The love that His followers show, Paul now says, should be the same."
Charles Caldwell Ryrie, Ryrie Study Bible: New American Standard Bible, 1995 Update, Expanded ed. (Chicago: Moody Press, 1995), 1836.