“In many and various ways God spoke of old to our fathers by the prophets, but in these last days he has spoken to us by a Son.” Christ, the Son of God made man, is the Father’s one, perfect and unsurpassable Word. In him he has said everything; there will be no other word than this one. St. John of the Cross, among others, commented strikingly on Hebrews 1:1-2:
In giving us his Son, his only Word (for he possesses no other), he spoke everything to us at once in this sole Word – and he has no more to say. . . because what he spoke before to the prophets in parts, he has now spoken all at once by giving us the All Who is His Son. Any person questioning God or desiring some vision or revelation would be guilty not only of foolish behaviour but also of offending him, by not fixing his eyes entirely upon Christ and by living with the desire for some other novelty.
From the Catechism of the Catholic Church 65