That we must not use detraction
In Solomon, in the Proverbs: “Love not to detract, lest you be taken away.” Also in the forty-ninth Psalm: “You sat, and spoke against your brother; and against the son of your mother you placed a stumbling-block.” Also in the Epistle of Paul to the Colossians: “To speak ill of no man, nor to be litigious.”
Source: The Treatises of Cyprian (New Advent)