It was the tale where Minamoto no Yoshiie chased after the "enemy," Sadato ABE, who abandoned and escaped from Koromogawa Seki (castle) and called out the lower line while aiming the arrow, to which, Sadato immediately shot back the top line of the song, so Yoshiie didn't shoot him due to the "sympathy of bushi (warrior)."
「敵」とは安倍貞任で、衣川関を捨てて敗走する安倍貞任を追う源義家が、矢を番えながら下の句を歌いかけると、貞任は即座にその上の句を返したので、義家は感じいって「武士の情け」と、矢を放つのを止めたという話。