“The litmus test of our love for God is our love of neighbor.”

Illustrated London News (16 July 1910)

Section 100
The Passionate State Of Mind, and Other Aphorisms (1955)
Context: The remarkable thing is that we really love our neighbor as ourselves: we do unto others as we do unto ourselves. We hate others when we hate ourselves. We are tolerant toward others when we tolerate ourselves. We forgive others when we forgive ourselves. We are prone to sacrifice others when we are ready to sacrifice ourselves.
It is not love of self but hatred of self which is at the root of the troubles that afflict our world.

Consistory of Cardinals: Exclusive Interview with Monsignor Felipe Arizmendi https://zenit.org/2020/11/27/consistory-of-cardinals-exclusive-interview-with-monsignor-felipe-arizmendi/ (27 November 2020)

Fifth Mansion, Ch. 3, translated by the Benedictines of Stanbrook (1921), revised and edited by Fr. Benedict Zimmerman (1930); reprinted (2003) by Kessinger Publications, p. 109
Interior Castle (1577)
Context: We cannot know whether we love God, although there may be strong reason for thinking so; but there can be no doubt about whether we love our neighbor or not. Be sure that, in proportion as you advance in fraternal charity, you are increasing your love of God, for His Majesty bears so tender an affection for us that I cannot doubt He will repay our love for others by augmenting, and in a thousand different ways, that which we bear for Him.

Letter to Dorothy Day, quoted in Catholic Voices in a World on Fire (2005) by Stephen Hand, p. 180.
Context: Our job is to love others without stopping to inquire whether or not they are worthy. That is not our business and, in fact, it is nobody's business. What we are asked to do is to love, and this love itself will render both ourselves and our neighbors worthy if anything can.

#64
Vectors: Aphorisms and Ten Second Essays (2001)

To Die Before Death: The Sufi Way of Life (1997)