Polish—alongside Czech, Slovak, and Sorbian—belongs to the West Slavic family of languages, which began to diverge from each other towards the end of the first millennium. Polish is the largest member by far of the Lechitic subgroup, which also includes Silesian and Kashubian.
The 13th-century Book of Henryków (księga henrykowska) contains, among other things, a chronicle of the monastery and surroundings of the village of Henryków in modern-day southwestern Poland. Like most such documents in medieval Europe, it was recorded in Latin, but it also attests the earliest known sentence written in a distinct Polish language—”in Polonico.”
An entry in the Book of Henryków from around 1270 has a certain villager, a Czech immigrant named Bogwalus, speaking with his wife:
bogwali · boemi uxor ſtabat ſepiſſime ad molam molendo
Cui uir ſuus idem · bogwalus · compaſſus · dixit · Sine ut ego etiam molam
hoc eſt in polonico · day ut ia pobruſa · a ti poziwai ·
The wife of Bogwalus the Bohemian very often used to stand grinding at the millstone.
This same husband of hers, Bogwalus, took pity on her and said, “Let me also grind”;
this is, in Polish, “day, ut ia pobrusa, a ti poziwai.”
The constraints of the Latin alphabet—since at the time there existed no standard orthography for writing the various West Slavic dialects—obscure the phonology somewhat. For example, the letter <i> is twice used for the central vowel /ɨ/, and <z>—which generally made the /ts/ sound in Medieval Latin, as it does in modern German—is employed for the retroflex affricate /tʂ/. The sentence has been reconstructed in modern Polish orthography as follows:
daj, ać ja pobruszę, a ty poczywaj.
daj dawać 2 sg prf imp ‘give!’ but here with the sense ‘allow, let … !’
ać is an exhortatory particle with the same function as modern niech; may be related to Old Church Slavonic аще ašte ‘if, whether, when’; it is an interesting coincidence that the scribe spells it <ut>, identical to the Latin word with which it more or less corresponds here.
ja … ty: the first- and second-person singular subject pronouns are used for contrast: “I do one thing, you do another.”
pobruszę pobruszyć 1 sg pres ind ‘grind’; the word is obsolete bruszyć (cf. Czech brousit ‘sharpen, hone’) with the prefix po-, which can indicate action for a short period of time; thus daj, ać pobruszę together means ‘let me grind for a little bit’; cf. the noun brus ‘whetstone.’
poczywaj poczywać 2 sg impv imp ‘rest’; the verb has been replaced by odpoczywać in the modern language.
Let me grind for a while, and you rest.