The Middle English mid-12th century round Sumer Is Icumen In (the manuscript of which is kept in the British Library, who have information on it here and here) is one of the earliest examples of a song in English that we have, and in the Middle English it fairly obviously rhymes (my favourite rhyme in it being "bulluc sterteþ, bucke uerteþ", which I think is roughly equivalent to rhyming "the bull starts" with "the deer farts").

I'm not entirely sure how accurately Richard Thompson's version of the song on YouTube here captures Middle English pronounciation - it's not my field - but the rhymes are pretty clear.