Athanasius said in his treatise on the Incarnation in 365 AD, "And when [Christ] says, "Father, if it be possible, let this chalice pass from Me; yet, not My will be done, but Yours;" and "the spirit is ready, but the flesh is weak," He gives evidence therein of two wills, the one human, which is of the flesh, and the other divine, which is of God. That which is human, because of the weakness of the flesh, shrinks from suffering. That, however, which is divine, is ready. Then too, Peter, hearing about the passion, says, "Cheer up, Lord;" but the Lord, chiding him, says, "Get behind me Satan; you are a scandal to Me, because you are mindful not of the things of God but of the things of men." This too, then, is to be understood in the suffering; but being God and, in accord with the divine substance, really being not subject to suffering, He readily accepts suffering and death" (Quotation from Faith of the Early Fathers by William Jurgens).
The Council of Chalcedon said, "Similarly we promulgate, according to the teaching of the Holy Fathers, that in Him are also two natural wills and two natural modes of working, unseparated, untransformed, undivided, unmixed; and these two natural wills are not opposed to each other as the impious heretics maintained." (Quoted from Ludwig Ott, "Fundamentals of Catholic Dogma," Denzinger 291)