It's always amazing what one "hears for the first time" -- especially when it's something that heard many times before. That is the way it was the other morning at Vigils during the second reading from a commentary on the Gospel of John by St. Cyril of Alexandria, bishop.
Until I "heard" this portion of the reading, I guess I never really thought about why Jesus was baptized by John. It said it in the scripture and so therefore it was important. The following portion of the text is worth pondering -- and giving God praise for His manifold mercy.
Christ "received the Spirit" in so far as he was man, and in so far as man could receive the Spirit. He do so in such a way that, thought he is the Son of God the Father, begotten of his substance, even before the incarnation, indeed before all ages, yet he was not offended at hearing the Father say to him after he had become man: You are my Son; today I have begotten you.
The Father says of Christ, who was God, begotten of him before the ages, that he has been "begotten today," for the Father is to accept us in Christ as his adopted children. The whole of our nature is present in Christ, in so far as he is man. So the Father can be said to give the Spirit again to the Son, though the Son possesses the Spirit as his own, in order that we might receive the Spirit in Christ. The Son therefore took to himself the seed of Abraham, as Scripture says, and became like his brothers in all things.(Source: The Liturgy of the Hours, Volume I - Advent Season, Christmas Season; Thursday after Epiphany to Baptism)