The "Old Testament" According to Origen

I've been reading Peter Martens 2012 monograph Origen and Scripture, an excellent account of Origen's encounter with scripture. The following passage comes from ch. 9, on the single message of the scriptures. Origen insisted--against some groups, such as gnostics--that both biblical testaments transmitted the same saving message.

Indeed, so concerned was Origen with the unity of this scriptural message that he could, on occasion, even balk at the twofold designation "Old" and "New" Testaments. In his ninth Homily on Numbers he remarks that the power of the gospel is also found in the law, its foundation, so that he does not give the name "Old Testament" to the law provided he understands it spiritually. "The law," Origen continues, "becomes an 'Old Testament' only for those who want to understand it in a fleshly way; and for them it has necessarily become old and aged, because it cannot maintain its strength. But," he strikingly concludes, "for us, who understand and explain it spiritually and in an evangelical sense, it is always new. Indeed, both are a 'New Testament' for us, not because of the age of time but because of the newness of understanding." (p. 203)