"The Lord has reigned from the Tree".
As Neale translates this stanza of the Vexilla Regis:
Fulfilled is all that David told
In true prophetic song of old;
Amidst the nations, God, saith he,
Hath reigned and triumphed from the Tree.
You will not find the words from the tree [literally, wood] in any version of the psalter that reposes upon your bookshelves ... nor in any translation ... unless you are lucky and learned enough to possess a copy of the 'Psalterium Romanum': where it does occur in verse 10 of psalm 96MT/AV=95LXX/Vg. This psalter was used by many in the time of Venantius, as well as much earlier. S Justin Martyr knew the reading a ligno, and accuses the Jews of deliberately censoring these words from their text because of the embarrassing Christian resonances. Tertullian, S Cyprian, Lactantius, and S Augustine knew it, but S Jerome could not find it in a Hebrew text. Nor is it in the Septuagint, except in one single bilingual manuscript ('apo xulou') where it might have crept across from the Latin side.
Despite this, could it be original? Well, the discovery of Hebrew Biblical manuscripts much earlier than the medieval Hebrew 'Masoretic text' which Jewry treats as authentic, has shown a much greater diversity in the textual tradition than most people expected ... especially in the poetic books. (I counted some 28 occasions on which the producers of the New Vulgate adopted a reading from the Qumran Isaiah, supported by early translations, in preference to a reading from the Masoretic Text.) And it has become very obvious (not least to that admirable Methodist Margaret Barker) that elimination of 'Christian' verses did occur. If this phrase is original, it could originally have referred to the wood of the ark of the Covenant, victorious over the Philistine god Dagon. That's quite a nice piece of typology anyway, isn't it?
This, however, is not in my view the big question. Texts , before the invention of printing, were inherently unstable (look at the apparatus criticus of the OCT Homer), and this phrase, 'original' or not, is quite simply part of our Biblical tradition (just as is the story in S John of the Woman Caught in Adultery); canonised by the Fathers who were fed by it ... and by the use of Venantius' hymn throughout the Latin Christian centuries. Dom Lentini, in his first draft of the revised Breviary hymns, retained the stanza, and admirably added in a footnote "We do not dare [audemus] to suppress the strophe nor to change the line". Good for him.
However, by the time the Liturgia Horarum was published, a more radical and philistine attitude held sway; a determination to 'dare' to make the Great Tradition less visible; a hermeneutic of rupture. It is the prayer of all right-thinking people that Papa Ratzinger has been successful in starting a process of turning the Philistines back. The restoration of this stanza to the Liturgy is overdue.