Charles and Louis met in February 842 near modern Strasbourg[4] to affirm their alliance by swearing a joint oath against Lothair.

The Oaths were not preserved in their original form; they were instead copied by the historian Nithard, another grandson of Charlemagne, in a work titled De Dissensionibus Filiorum Ludovici Pii "On the Quarrels of Louis the Pious's Sons".

Louis the German's oath is recorded as follows:Pro Deo amur et pro christian poblo et nostro commun saluament, d'ist di en auant, in quant Deus sauir et podir me dunat, si saluarai eo cist meon fradre Karlo, et in adiudha et in cadhuna cosa, si cum om per dreit son fradra saluar dift, in o quid il mi altresi fazet.

The army of Charles the Bald swore that:Si Lodhuvigs sagrament, que son fradre Karlo iurat conservat, et Karlus meos sendra de suo part non los tanit, si io returnar non l'int pois, ne io ne neuls, cui eo returnar int pois, in nulla aiudha contra Lodhuvig nun li iv er.

Charles the Bald is recorded as saying:In Godes minna ind in thes christianes folches ind unser bedhero gealtnissi, fon thesemo dage frammordes, so fram so mir Got geuuizci indi mahd furgibit, so hald ih tesan minan bruodher, soso man mit rehtu sinan bruodher scal, in thiu, thaz er mig sosoma duo ; indi mit Ludheren in nohheiniu thing ne gegango, zhe minan uuillon imo ce scadhen uuerhen.

The soldiers of Louis the German replied: Oba Karl then eid, then er sinemo bruodher Ludhuuuige gesuor, geleistit, indi Ludhuuuig min herro, then er imo gesuor, forbrihchit, ob ih inan es iruuenden ne mag, noh ih noh thero nohhein, then ih es iruuenden mag, uuidhar Karle imo ce follusti ne uuirdit.

[10] According to Hall, the text does not contain any particular features that would mark it as belonging to the future Oïl or Oc groups, with the possible exception of the form tanit 'keep' < *tɛ́ni̯at, which is characteristic of Lorraine.

[11] The difficulty of discerning a particular dialect in the text[12] may be due to a deliberate effort by the author to write in a sort of regional koiné.

sí loðuvíks saɣramɛ́nt kə son fráðrə kárlə dʒurát konsɛ́rvat e kárləs mɛ́əs sɛ́ndrə də sóə párt non lə s tánət sí jɔ́ rətornár non lént pɔ́i̯s nə jɔ́ nə nəúls kui ɛ́ə rətornár ént pɔ́i̯s en núla ajúða kɔ́ntra loðuvíg nón li iv ɛ́r Here are the Romance sections of folio 13r along with digital facsimiles: