שנו חכמים בלשון המשנה, ברוך שבחר בהם ובמשנתם
Our Sages taught in the words of the Mishnah; blessed is He Who chose them and their Mishnayos
In all standard Siddurim that I’ve seen, this phrase is used to introduce the “sixth Perek” of Avos. This is also the phraseology used here. The only variation I’ve seen is that occasionally רבותינו is used instead of חכמים.
Why is this phrase included? The first half I understand: as תנו in Aramaic is the same as שנו in Hebrew, the more verbose שנו חכמים בלשון המשנה would seem to be equivalent to the Gemara’s תנו רבנן, as both introduce Braisos.
What I don’t understand is the second half of the phrase. Why do we mention here, specifically, “Blessed is He Who chose them and their Mishnayos”? What relevance does that have to here, especially as the first half establishes that this isn’t actually a Mishnah?