From Book I, chapter 2.  Harrington wrote,

THAT part of the preliminarys which the prevaricator, as is usual with him, recites in this place falsly and fraudulently, is thus: relation had to these two times (that of antient and that of modern prudence) the one,…, ending with the liberty of Rome, the other beginning with the arms of Cæsar (which extinguishing liberty, became the translation of antient into modern prudence, introduc’d in the ruin of the Roman empire by the Goths and Vandals)

GOVERNMENT (to define it de jure, or according to antient prudence) is an art wherby a civil society of men is instituted and preserv’d, upon the foundation of common right or interest; or (to follow Aristotle and Livy) it is an empire of laws, and not of men.

AND government, to define it de facto, or according to modern prudence, is an art wherby som man, or som few men, subject a city or a nation, and rule it according to his or their privat interest; which, because laws in such cases are made according to the interest of a man, or som few familys, may be said to be an empire of men, and not of laws.

Hereby it is plain, whether in an empire of laws, and not of men, as a commonwealth; or in an empire of men, and not of laws, as monarchy: first,
That law must equally procede from will, that is, either from the will of the whole people, as in a commonwealth; from the will of one man, as in an absolute, or from the will of a few men, as in a regulated monarchy.

For the key phrase ‘of laws’ taken up into the Constitution of Massachusetts see here.