John Chrysostom

(Hom. xv. [xiv.] 1.) In this complete sense only the Son and the Holy Ghost see the Father. For how can created nature see that which is uncreated? So then no man knoweth the Father as the Son knoweth Him: and hence what follows, The Only-Begotten Son, Who is in the bosom of the Father, He hath declared Him. That we might not be led by the identity of the name, to confound Him with the sons made so by grace, the article is annexed in the first place; and then, to put an end to all doubt, the name Only-Begotten is introduced.