Ambrose of Milan — as excerpted in the Catena Aurea on Luke 3:21-22

“We have seen the Spirit, but in a bodily shape, and the Father whom we cannot see we may hear. He is invisible because He is the Father, the Son also is invisible in His divinity, but He wished to manifest Himself in the body. And because the Father did not take the body, He wished therefore to prove to us that He was present in the Son, by saying, Thou art my Son.”