ながながと川一筋や 雪の原
haikus are hard to translate accurately but its basically likening a river in the early dawn that cuts through fresh snowy plains to the initial stroke of ink on a blank piece of parchment having been written by the heavens
written by Banchō(凡兆), a student of the most established poet in Edo, Basho - Banchō was less serious than his peers and much like the characters in his name, he became 'mediocre'