J.I. Packer on Loving Christians

"Love to one another...is the family likeness of God's children; he who does not love Christians is evidently not in the family, for 'God is love' and imparts a loving nature to all who know him (1 John 4:7-8). But 'God is love is a vague formula; how can we form a clear idea of the love that God would reproduce in us? 'This is how God showed his love among us: he sent his one and only Son into the world that we might live through him' (1 John 4:9). Nor was this God's acknowledgment of some real devotion on our part; not at all. 'Herein is love, not that we loved God but that'- in a situation where we did not love him, and there was nothing about us to move him to do anything other than blast and blight us for our ingrained irreligion- 'he loved us, and sent his Son to be the propitiation [wrath bearing sacrifice] for our sins.' By this divine initiative, says John, the meaning and measure of the love that we must imitate are made known."
-J.I. Packer (In My Place Condemned He Stood, 37)