Ora et labora: No Benedictine motto

In these pedagogical texts of the late 18th and the 19th centuries "no reference to monasticism can be detected.
     "By contrast, it says in the programmatic text Praecipua Ordinis Monastici Elementa [(1880)], by Archabbot Maurus Wolter [(1824-1890)],

Hinc vetus clarissimaque illa monachorum tessera:  Ora et labora.  Opus Dei atque opus laboris, . . . sive alae duae, quae ad altissimam attollunt perfectionem . . . ut haec illi vigoris, illa huic benedictionis semper novum afferat incrementum.

Maurus Wolter gives no source. . . .  The striking parallels make it plain that he was influenced by the [late 18th- and the 19th-century] pedagogical literature on the theme of prayer and work.
     "The ongoing treatment [(Die bis heute anhaltende Wertung)] of ora et labora as a motto of the Benedictine order shows how much of an impact Maurus Wolter had on the understanding of his time, such that this treatment [(dies)] could be so deeply rooted [still today].  But we should ask whether what lies here before us [in the ora et labora] is for Benedictine life today an appropriate leitmotif or an unhappily constrictive foreshortening [(eine unglückliche Verkürzung)]."

     Oliver J. Kaften, OSB, "Ora et labora:  (k)ein benediktinishes Motto [a, or, rather, no Benedictine motto]:  eine Spurensuche," Erbe und Auftrag 90 (2014):  421 (415-421), translation mine.  These concluding words are preceded by an unsuccessful attempt to find anything closely resembling the (supposedly reductive) motto before the late medieval (but especially the modern and even Protestant) period (though I certainly do not summarize those findings properly here).