John Owen, vol. 12, Vindication of the Gospel, chapter 27, p. 497:
It is true, the will of God the Father, Son, and Holy Ghost, is but one. It is a natural property, and where there is but one nature there is but one will: but in respect of their distinct personal actings, this will is appropriated to them respectively, so that the will of the Father and the will of the Son may be considered [distinctly] in this business; which though essentially one and the same, yet in their distinct personality it is distinctly considered, as the will of the Father and the will of the Son. Notwithstanding the unity of essence that is between the Father and the Son, yet is the work distinctly carried on by them; so that the same God judges and becomes surety, satisfieth and is satisfied, in these distinct persons.
Thus though this covenant be eternal, and the object of it be that which might not have been, and so it hath the nature of the residue of God’s decrees in these regards, yet because of this distinct acting of the will of the Father and the will of the Son with regard to each other, it is more than a decree, and hath the proper nature of a covenant or compact.