If anyone maintain that men ought to be compelled by fire and sword to profess certain doctrines, and conform to this or that exterior worship, without any regard had unto their morals; if anyone endeavor to convert those that are erroneous unto the faith, by forcing them to profess things that they do not believe and allowing them to practice things that the Gospel does not permit, it cannot be doubted indeed but such a one is desirous to have a numerous assembly joined in the same profession with himself; but that he principally intends by those means to compose a truly Christian Church is altogether incredible. It is not, therefore, to be wondered at if those who do not really contend for the advancement of the true religion, and of the Church of Christ, make use of arms that do not belong to the Christian warfare. If, like the Captain of our salvation, they sincerely desired the good of souls, they would tread in the steps and follow the perfect example of that Prince of Peace, who sent out His soldiers to the subduing of nations, and gathering them into His Church, not armed with the sword, or other instruments of force, but prepared with the Gospel of peace and with the exemplary holiness of their conversation. This was His method. Though if infidels were to be converted by force, if those that are either blind or obstinate were to be drawn off from their errors by armed soldiers, we know very well that it was much more easy for Him to do it with armies of heavenly legions than for any son of the Church, how potent soever, with all his dragoons.
Source: John Locke. A Letter Concerning Toleration, paragraph 2, October 3, 1689. Daily Dabble in the Classics is compiled, and edited (with occasional commentary) by The Moral Liberal, Editor In Chief, Steve Farrell.