“Worse than sin against God is sin against man.”
Source: The Sayings and Teachings of the Great Mystics of Islam (2004), p. 29
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Sufyan al-Thawri 9
Muslim Scholar and founder of Thawri Madhhab 716–778Related quotes

As quoted in The New York Times (3 November 1986)

§ IV
1910s, At the Feet of the Master (1911)
Context: Of all the Qualifications, Love is the most important, for if it is strong enough in a man, it forces him to acquire all the rest, and all the rest without it would never be sufficient. Often it is translated as an intense desire for liberation from the round of births and deaths, and for union with God. But to put it in that way sounds selfish, and gives only part of the meaning. It is not so much desire as will, resolve, determination. To produce its result, this resolve must fill your whole nature, so as to leave no room for any other feeling. It is indeed the will to be one with God, not in order that you may escape from weariness and suffering, but in order that because of your deep love for Him you may act with Him and as He does. Because He is Love, you, if you would become one with Him, must be filled with perfect unselfishness and love also.
In daily life this means two things; first, that you shall be careful to do no hurt to any living thing; second, that you shall always be watching for an opportunity to help.
First, to do no hurt. Three sins there are which work more harm than all else in the world — gossip, cruelty, and superstition — because they are sins against love. Against these three the man who would fill his heart with the love of God must watch ceaselessly.
Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 546.

The Tragic Sense of Life (1913), IV : The Essence of Catholicism
Context: The real sin — perhaps it is a sin against the Holy Ghost for which there is no remission — is the sin of heresy, the sin of thinking for oneself. The saying has been heard before now, here in Spain, that to be a liberal — that is, a heretic — is worse than being an assassin, a thief, or an adulterer. The gravest sin is not to obey the Church, whose infallibility protects us from reason.

“Anything done against faith or conscience is sinful.”
Commentary on Romans, cap 14, I 3