For if the word spoken by angels - The revelation in the Old Testament. It was indeed given by Yahweh, but it was the common opinion of the Hebrews that it was by the ministry of angels; see Acts 7:38, Acts 7:53 notes, and Galatians 3:19 note, where this point is fully considered. As Paul was discoursing here of the superiority of the Redeemer to the angels, it was to the point to refer to the fact that the Law had been given by the ministry of angels.
Was steadfast - Was firm - βέβαιος bebaios; settled - established. It was not vacillating and fluctuating. It determined what crime was, and it was firm in its punishment. It did not yield to circumstances; but if not obeyed in all respects, it denounced punishment. The idea here is not that everything was “fulfilled,” but it is that the Law so given could not be violated with impunity. It was not safe to violate it, but it took notice of the slightest failure to yield perfect obedience to its demands.
And every transgression - Literally, “going beyond, passing by.” It means every instance of “disregarding” the Law.
And disobedience. - Every instance of “not hearing” the Law - παρακοὴ parakoē - and hence, every instance of disobeying it. The word here stands opposite to “hearing” it, or attending to it - and the sense of the whole is, that the slightest infraction of the Law was sure to be punished. It made no provision for indulgence in sin; it demanded prompt, implicit, and entire obedience. “Received a just recompense of reward.” Was strictly punished. Subjected to equal retribution. This was the character of the Law. It threatened punishment for each and every offence, and made no allowance for transgression in any form; compare Numbers 15:30-31.