Who being the brightness of His glory and the express image of His person, and upholding all things by the word of His power, when He had by Himself purged our sins, sat down at the right hand of the Majesty on high,
having become so much better than the angels, as He has by inheritance obtained a more excellent name than they.
For to which of the angels did He ever say:
"You are my Son,
Today I have begotten You"?
"I will be to Him a Father,
And He shall be to Me a Son"?
Christ is the only-begotten of the Father, Begotten of the Father before all ages.
So in this sense, Christ receives his inheritance and in receiving his inheritance becomes more glorious than the angels. But because he is begotten before all ages, there is no time when he was not yet begotten, when he had not yet received his inheritance, when he had not yet become more glorious than the angels. There is an after but not a before.
Paul is reinforcing his claim with quotations from the Jewish Scripture, as evidence that God has spoken of a Son greater than the angels-- for even the angels are not sons begotten of the Father. He's prepping the Jews for the Incarnation by pointing out Incarnational promises in their own Scripture.
Chrysostom uses a highly detailed examination of this passage to provide evidence against both Sabellianism and Arianism. That is to say, on the one hand he argues against the idea that Christ is unoriginate and indistinct from the Father, and on the other hand against the notion that Christ is a created being, nonexistant before the Incarnation.
As the one who "upholds all things by the word of his power," Christ is clearly not a created being. And yet by himself coming among us to purge our sins by his inheritance, Christ is clearly distinct from God the Father.
And as we emulate Christ's condescension, Chrysostom exhorts us also to "take the form of a slave" and be humble. If we take pride in anything, says Chrysostom, we should be proud of our poverty.