Gregory I, Pope. [Letter to Theodelind, queen of the Lombards, 598] in Gregorii I papae Registrum epistolarum 9.67, 2.87-88

[Letter to Pope Gregory I to Theodelind, queen of the Lombards]
Gregory thanks the queen for her work in the cause of peace and encourages her to keep her husband from renouncing his alliance with the Christian republic (the papal state). Paul the Deacon cites this letter in History of the Lombards, 4.9, along with a letter to the king, Agilulf, thanking him for ordering the peace, saying he shows by loving peace that he loves God, since otherwise the blood of poor rural areas would have been shed with sin and danger, areas whose labor is of use to both of us, and asks him to announce the peace to his dukes by letter (9.66).
Online at Epistolae (See also Bibliographia record).