“The entire law is summed up in a single command:
“Love your neighbor as yourself.”
“This statement is expressed in a beautiful and powerful way: “Love your neighbor as yourself.” There is no attitude more outstanding, respected, and virtuous than love. No one can show you a model that is better, more certain, and more real than yourself.
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If you want to know how to love your neighbor and want to have a clear example of it, then pay careful attention to how you love yourself. In times of need and danger, you certainly want to be loved and helped with all the advice, resources, and power of everyone everywhere. So you don’t need a book to teach and admonish you how to love your neighbor. For you have the best and most lovely book about all laws right in your heart.
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You don’t need a teacher; just consult your own heart. It will thoroughly teach you that your neighbor should be loved the way you love yourself. Further, love is the highest virtue. Its prepared to serve not only with words, hands, money and possessions, but also with the body and even life itself. It’s not motivated by reward or anything else. It’s not slowed down by unworthiness or ungratefulness of a neighbor. We should serve our neighbor out of love, just as a mother cherishes and cares for her child out of love.”
Taken from Faith Alone: A Daily Devotional (Writings of Martin Luther)