Cyril of Alexandria

Now whereas He possesses every good in abundance, why does He pray, since He is full, and has altogether need of nothing? To this we answer, that it befits Him, according to the manner of His dispensation in the flesh, to follow human observances at the time convenient for them. For if He eats and drinks, He rightly was used to pray, that He might teach us not to be lukewarm in this duty, but to be the more diligent and earnest in our prayers.