These two lines of lyrics come from the song "For Whom".

According to the query of Kugou Music, the song "For Whom" was written by Zou Youkai, composed by Meng Qingyun, and sung by Zu Hai. It was released on September 1, 2004. Zu Hai was born on May 10, 1976 in Bengbu City, Anhui Province, China. She graduated from the China Conservatory of Music. She is a female singer of ethnic singing in mainland China and a national first-class actor.

The classic part of the song is "The mud is wrapped around the trouser legs, and the back of the clothes is soaked with sweat. I don't know who you are, but I know who you are for, who you are for, who you are for, and the harvest of autumn."