God, the supreme Lord and King of all the world, hath ordained civil magistrates to be under him, over the people, for his own glory and the public good; and to this end hath armed them with the power of the sword, for defence and encouragement of them that do good, and for the punishment of evil doers.
Rom 13.1-Rom 13.4
It is lawful for Christians to accept and execute the office of a magistrate when called there unto; in the management whereof, as they ought especially to maintain justice and peace, according to the wholesome laws of each kingdom and commonwealth, so for that end they may lawfully now, under the New Testament wage war upon just and necessary occasions.
2 Sam 23.3, Ps 82.3-Ps 82.4, Luke 3.14
Civil magistrates being set up by God for the ends aforesaid; subjection, in all lawful things commanded by them, ought to be yielded by us in the Lord, not only for wrath, but for conscience sake; and we ought to make supplications and prayers for kings and all that are in authority, that under them we may live a quiet and peaceable life, in all godliness and honesty.
Rom 13.5-Rom 13.7, 1 Pet 2.17, 1 Tim 2.1-1 Tim 2.2