9 Thus the greater number of them will not allow Him to have the impossible nature of God because He feared His Passion and showed Himself weak by submitting to suffering. They assert that He Who feared and felt pain could not enjoy that confidence of power which is above fear, or that incorruption of spirit which is not conscious of suffering: but, being of a nature lower than God the Father, He trembled with fear at human suffering, and groaned before the violence of bodily pain.
These impious assertions are based on the words, My soul is sorrowful even unto death, and “Father if it be possible let this cup pass away from Me”, and also, My God, My God, why have You forsaken Me ? to which they also add, Father into Your hands I commend My Spirit. All these words of our holy faith they appropriate to the use of their unholy blasphemy: that He feared, Who was sorrowful, and even prayed that the cup might be taken away from Him; that He felt pain, because He complained that God had deserted Him in His suffering; that He was infirm, because He commended His Spirit to the Father.
His doubts and anxieties preclude us, they say, from assigning to Him that likeness to God which would belong to a nature equal to God as being born His Only-begotten. He proclaims His own weakness and inferiority by the prayer to remove the cup, by the complaint of desertion and the commending of His Spirit.
Source: On the Trinity (New Advent)