"you will find much more labouring amongst the woods than you ever will amongst books."

"aliquid amplius invenies in silvis quam in libris."

     St. Bernard of Clairvaux, Epistola 106 ad Magistrum Henricum Murdac,  Sämtliche Werke lateinisch/deutsch 2, ed. Gerhard B. Winkler (Innsbruck:  Tyrolia-Verlag, 1992), 772 (770-774 even).  =Sancti Bernardi opera 3 (1963) or 7 (1974).  English from The letters of St. Bernard of Clairvaux, trans. Bruno Scott James (Cistercian Publications, 1998 [1953]), 156 (155-156), in which this appears as Letter 107.

     As to the nefariously illegitimate uses to which this seems likely to be put, see the note on pp. 1104-1105 of Sämtliche Werke lateinisch/deutsch 2:

When Bernard invites Murdac into the monastic life, he has the latter's position [(dessen Situation)] as teacher in mind, and sets before him a [form of] learning [(Wissen)] that is other than that which one gets from books:  'amplius invenies in silvis quam in libris.'  It may seem that here a mystical view of nature emerges, namely, the recognition that [nature (sie)] has the capacity to prompt thoughts that lead to God:  'Ligna et lapides docebunt te.'  Clearly this is an awareness of another kind than that of theology ('quod a magistris audire non possis') and of the Bible itself, an awareness that arises [(sich regt)] and becomes living in the enchanted stillness of the forest.  Perhaps[, however,] Bernard meant [(wollte)] by this not quite that precisely, even if he didn't exclude it either.  Perhaps the stillness of the forest is [a] symbol for that inner stillness in which the soul discovers its likeness to God.  Perhaps he understood thereunder also a [form of] learning [(Wissen)] that is wisdom above all, i.e. the experience of God, [and] therefore the desire for God and [for a] perfect [form of] learning [(Wissen)] about him.  See on this theme E. Gilson, "Sub umbris arborum," Medieval studies 14 (1952):  149-151.  These words made also an impression upon Petrarch, who took them up in De vita solitaria II.3.14, where he laments having never had this experience.  Rancé, too, took them up in turn, as a way of demonstrating (but of course unjustly) that Bernard had never studied books.  'Car pour l’étude, il ne s’y est jamais appliqué comme il l’a avoué lui-même' (Réponse au traité des études monastiques, Paris 1692, 31).

Translation and underscoring mine.
     If I had to guess, I, too, would be inclined to look for a more or less figurative sense for "woods" (perhaps those bordering "the open pastures of the Gospels' rather than those on 'the mountain sides" from which Christ has "leapt"), and assume that by "words" Bernard meant something more like the bare text of “the Prophets” as read by “Jewish hacks".  Or something like that.

     Thanks to Lugene Schemper for introducing me to this one.