Eusebius of Vercelli

You must choose one of two paths. Either there is a single inequality in the two [divine Father and divine Son] or there is a single equality in the glory of divinity itself. For no one is either greater or less than his own form.… This singular equality is seen not only in the concord of their willing together. It is rather in their very deity, since the form of equality is in no way divided into parts. Where there is one equality, there is no discord. Where there is one equality, neither is prior to the other. Neither is posterior nor subordinate, since there is no distinction in the united equality, which is the fullness of divinity.

How then did he “empty himself”? When the “form of God accepted the form of a slave,” when he who is preeminently the Lord deigned to take on himself what belongs to a slave. The Word was made flesh by bearing and doing what was beneath him in his indulgence and compassion toward us. All that he possessed by nature is emptied into this his person. Having been made obedient as a man in the true “fashion of humanity,” he has restored to our nature by his own humility and obedience what had perished through disobedience in Adam.